Class Reunion Memorial Ideas: Honoring Classmates and Preserving Memories Through Displays

| 13 min read

Every class reunion carries a quiet weight alongside the celebration. Somewhere between the name tags and the banquet tables, someone asks about a former classmate who is no longer here — and that question deserves an answer worthy of the person being remembered. Class reunion memorial ideas range from a simple printed tribute page to a full interactive digital display, but the best approaches share one characteristic: they treat the people being honored as individuals whose stories still matter, not just names on a list.

This guide walks through practical approaches for building a reunion memorial — from gathering content and designing the display to setting up a tribute station that gives attendees real time to reflect. Whether you are planning a 10-year reunion or a 50th, these ideas can be adapted to your group size, budget, and venue.

Planning a reunion memorial is an act of care for both the living and the deceased. When classmates see a thoughtful tribute to someone they knew, it signals that this reunion honors the whole story of a graduating class — including the chapters that ended too soon.

Visitors reading wall of honor interactive display with eagle and flag graphics

Interactive memorial displays give reunion attendees a dedicated space to remember classmates, engage with shared history, and pay their respects in a dignified setting

Why Class Reunion Memorials Matter

A memorial at a class reunion does several things that a moment of silence alone cannot accomplish. It gives names and faces to the people being honored. It provides context — who they were, what they meant to the class, what they achieved or contributed. And it creates a space where grief and gratitude can coexist with the celebration around it.

Reunions frequently serve as the only occasion when a graduating class comes together in one place. For many attendees, it is the one time every five or ten years when remembering a lost classmate feels collectively appropriate. A memorial display makes that remembrance possible without requiring anyone to interrupt the event — it stands on its own, available to anyone who wants to approach it.

Schools and alumni organizations that have built digital recognition infrastructure understand this well. Guidance on honoring fallen soldiers with memorial recognition translates directly to reunion memorial contexts: the principles of dignified display, thoughtful content, and lasting accessibility all apply whether honoring veterans or classmates.

Before You Start: What You Need to Gather

The quality of any memorial display depends on the content behind it. Collecting that content is the first task, and it takes more time than most reunion planners expect.

What to collect for each person being honored:

  • Full name and graduation year (and maiden name, if applicable)
  • Dates of birth and passing
  • A photograph — ideally a yearbook photo and, if available, a photo from later in life
  • A brief life summary: career, family, passions, community involvement
  • A quote or memory contributed by classmates or family

Sources for this content:

  • Your class yearbooks (scan relevant pages or request digital copies)
  • Alumni association records and past reunion directories
  • Families of the deceased, reached through classmate networks
  • Obituaries from local newspapers
  • Class Facebook groups or email lists soliciting memories

Give yourself at least six weeks to gather content before the reunion. The families of deceased classmates deserve a respectful, unhurried contact — not a last-minute request that feels transactional.

If you are working from older yearbooks, digitizing old yearbooks for hall of fame displays walks through how to convert physical pages into high-quality digital assets suitable for display. The same workflow applies directly to reunion memorial production.

Class Reunion Memorial Display Ideas

1. Printed Memory Board

The most accessible option for any budget. A printed memory board — typically foam core or a banner-printed display — features each honoree’s photo, name, years of life, and a brief tribute. This works well for smaller classes or reunions where a digital setup is impractical.

What makes it effective:

  • Consistent formatting for all honorees (same photo size, same type treatment)
  • A clear, dignified title: “In Memory Of” or “We Remember” followed by the class year
  • Space for a small quote or memory beneath each name
  • High-resolution printing — faces must be clearly recognizable

What to avoid: A crowded layout that forces faces into thumbnail size, inconsistent photo quality that makes some honorees look like afterthoughts, and glossy paper that creates glare under event lighting.

2. Memory Table with Physical Artifacts

A memory table combines printed materials with physical objects — flowers, candles, copies of the yearbook, a guest memory book — to create a tangible tribute space. This approach works especially well for milestone reunions (25th, 50th) where the class has strong shared memories and enough history to fill a table meaningfully.

Suggested memory table elements:

  • Framed individual portraits or a printed memorial booklet attendees can take home
  • An open guest memory book where attendees can write tributes
  • Yearbooks from the graduation year, open to relevant pages
  • A single flower or candle for each person being honored
  • A QR code linking to an online tribute page or digital slideshow

3. Video or Slideshow Memorial Tribute

A video tribute played during the event — typically during dinner or at a dedicated moment in the program — can reach every attendee simultaneously. It works best as a respectful, unhurried sequence: one or two slides per person, with their photo, name, and brief tribute displayed long enough to read and absorb.

Production guidance:

  • Allow 8–12 seconds per person — enough to read the name and tribute without rushing
  • Use a simple, dignified design: dark background, light type, one strong photo
  • Choose instrumental background music rather than songs with strong associations that might distract
  • Keep the total runtime under 10 minutes for most class sizes — long enough to feel complete, short enough to hold attention

For examples of tribute language, short memorial tribute samples for honoring someone special provides frameworks adaptable to any individual’s background and story.

Visitor pointing at interactive hall of fame screen in school lobby

Touchscreen memorial displays allow attendees to navigate at their own pace — exploring individual tribute pages, viewing photos, and reading memories without waiting for a scheduled program moment

4. Interactive Touchscreen Memorial Display

For reunions that want to offer the most complete, dignified memorial experience, an interactive touchscreen display is the highest-impact option. Rather than showing all honorees at once (as a printed board does) or sequentially (as a slideshow does), a touchscreen lets each attendee navigate to the people they knew personally and spend as much or as little time there as they need.

What a touchscreen memorial display can include:

  • Individual profile pages for each honoree with photos, biography, and tribute text
  • A gallery of yearbook photos and candid images from the class’s school years
  • Submitted memories and tributes from classmates, displayed as cards or quotes
  • A timeline of the class’s history that contextualizes when each person was part of it
  • A digital condolence feature where attendees can leave a note that the family receives

The interactivity removes the social awkwardness of standing in front of a static display for several minutes — attendees can engage privately, at their own pace, which encourages more genuine reflection.

Organizations like Rocket Alumni Solutions build touchscreen wall systems that schools and alumni groups deploy for exactly this kind of recognition. The same content infrastructure used for athletic halls of fame and institutional histories can be adapted for reunion memorial displays.

Understanding what makes touchscreen presentations effective helps when designing any digital memorial. Research on designing touch screen experiences for user engagement covers navigation design, content hierarchy, and interface choices that apply directly to memorial display contexts.

5. Candle Lighting or Moment of Silence Integration

Whatever physical display format you choose, consider pairing it with a brief, structured moment in the event program. A candle lighting ceremony — where attendees are invited to light a candle in honor of a classmate — or a 60-second moment of silence gives the memorial display a formal acknowledgment that elevates its significance.

Program moment guidelines:

  • Announce it clearly in advance in reunion communications so attendees are prepared
  • Have a designated speaker (class president, reunion committee chair, or a volunteer who knew the honored classmates well) read the names
  • Keep it brief — 3 to 5 minutes maximum — and transition out of it gracefully into the celebration
  • Invite attendees to visit the memorial display throughout the evening

Building a Memorial That Lasts Beyond Reunion Night

One of the most valuable things a reunion committee can do is design the memorial in a way that extends beyond the event itself. The content gathered — photos, biographies, tribute text, classmate memories — represents a significant effort that should not disappear after one night.

Options for preserving the memorial:

  • A class memorial website or dedicated page within an alumni association site
  • A digital archive contributed to the school’s alumni office
  • A printed memorial booklet mailed to all registered alumni after the reunion
  • Contributing tribute content to a school’s interactive hall of fame display that remains on campus year-round

Schools that maintain interactive institutional histories — including class histories with class-by-class recognition — can incorporate reunion memorial content into permanent displays. Guidance on developing college history timelines covers how institutions build comprehensive timelines that include this kind of legacy content from individual classes.

Two men viewing blue hawk hall of fame digital display together

Memorial displays that remain accessible after the reunion itself — through an online version, a school archive, or a permanent campus installation — extend the value of the content gathered for the event

Making Your Memorial Inclusive and Accurate

Two commitments matter more than any design decision: accuracy and inclusivity.

Accuracy means confirming that every person listed has actually passed, confirming the correct spelling of every name, and verifying dates against reliable sources. Listing someone as deceased who is still living — a mistake that happens when working from outdated or secondhand information — is deeply distressing for that person and their family. Verify every name before the display is finalized.

Inclusivity means honoring every classmate who has passed regardless of how prominent they were in school. The valedictorian and the student no one knew well both deserve equal care on a memorial display. If you have complete yearbook records, use them as your source for who graduated with the class. Do not rely on memory or informal networks alone.

Some reunions struggle with geographic or demographic gaps in their alumni networks that make it harder to learn about classmates from certain communities. Reaching out through multiple channels — not just the main class email list — helps ensure completeness.

Coordinating Memorial Content With the School

If your reunion is associated with a school that maintains alumni records or digital recognition systems, connect with the alumni office early. They may have:

  • Obituary archives or alumni death records that confirm your list
  • Yearbook scan archives that provide higher-resolution photos than individual copies
  • Existing digital infrastructure where tribute content could live permanently
  • Contacts who can connect you with families of deceased classmates

Schools with existing digital recognition systems often already document notable alumni through interactive displays. Insights on how digital hall of fame and donor wall dual-purpose systems are structured show how the same platform can serve recognition and memorial purposes simultaneously — a model worth proposing to your school if one does not exist yet.

Man pointing at red Trojan wall of honor digital display in school hallway

Schools with permanent wall-of-honor installations provide an ideal permanent home for reunion memorial content — extending tribute displays beyond a single event and making them accessible to future students and visitors

Exploring Best-in-Class Digital Platforms

If you are evaluating digital display solutions for a reunion memorial, comparing platforms by capability rather than cost alone gives you a clearer decision framework. Best digital showcase platforms in 2025 covers how to evaluate platforms against key criteria: content management flexibility, content longevity, navigation design, and deployment options for both event and permanent settings.

For reunions that want a temporary setup — a display active only for the event weekend — renting or borrowing a touchscreen and loading it with pre-built content is viable. For reunions interested in contributing to a permanent school installation, consulting with the school’s facilities and IT teams ensures the content format is compatible with existing systems.

Touchscreen hall of fame showing Emily Henderson track hurdles athlete profile

Individual profile pages on touchscreen displays — whether for athletic recognition or class reunion memorials — follow the same structure: portrait photo, name, dates, and tribute content organized for easy navigation

Pre-Reunion Memorial Planning Checklist

Use this checklist to track your memorial preparation across the months before your reunion.

Content gathering (8–12 weeks before)

  • Pull complete class roster from graduation year records
  • Cross-reference with alumni association death records and obituaries
  • Contact classmate network (email list, Facebook group) to confirm additional names
  • Compile names, dates of birth/passing, and brief biographies for each honoree
  • Request family permission for photos and tribute content
  • Digitize yearbook photos at 300 dpi minimum for print quality

Display production (4–6 weeks before)

  • Select display format: printed board, slideshow, touchscreen, or combination
  • Design layout template for consistent honoree treatment
  • Write or compile tribute text for each honoree (100–200 words each)
  • Proofread all names, dates, and tribute text — have a second person verify
  • Order or produce the physical display; allow lead time for printing or device setup

Event setup (1 week before)

  • Confirm display placement in the venue — quiet, accessible, well-lit, separate from high-traffic areas
  • Test any digital or AV equipment on-site
  • Confirm program moment with event MC or speaker
  • Prepare a guest memory book and signage for the memorial station
  • Notify attendees via final communications that a memorial display will be present

Post-reunion (within 2 weeks after)

  • Archive all memorial content in a digital format for future use
  • Send tribute content to families of honorees who participated
  • Contact school alumni office about contributing to a permanent display
  • Note lessons for the next reunion committee

Connecting Memorial Displays to Broader Alumni Recognition

Reunion memorial ideas do not exist in isolation. The strongest alumni engagement programs treat memorial recognition as one element of a larger system that celebrates the full arc of a class’s history — athletic achievements, academic honors, service, and legacy.

For alumni organizations looking at how physical display design can carry both celebratory and memorial recognition in the same space, guidance on sports memorabilia and alumni display design shows how schools integrate multiple content types into cohesive wall systems that serve different audiences and purposes.

For memorial displays specifically tied to veterans, service members, and community heroes, memorial flag display cases and school veterans tribute walls covers specialized design approaches that honor military service within alumni recognition contexts.

Conclusion

A class reunion memorial does not need to be elaborate to be meaningful. What matters most is that the people being honored are treated with the same care and specificity as they would have been in life — individual names, individual faces, individual stories. Whether you build a simple printed board or deploy a full interactive touchscreen display, the standard is the same: every person on that display should be recognizable as a real individual, not a statistic.

Start with your content. Give yourself enough time to gather it carefully. Then choose the format that fits your resources and venue. The attendees who approach that display on reunion night — whether to find a childhood friend, a teammate, or someone they barely knew but mourn all the same — will feel the difference between a memorial made with care and one assembled at the last minute.

Build a Memorial Display That Honors Every Classmate

Rocket Alumni Solutions creates interactive touchscreen displays for schools and alumni organizations — including tribute walls, class history timelines, and memorial recognition systems that extend far beyond a single reunion night.

Explore Memorial Display Solutions

Explore Insights

Discover more strategies, guides, and success stories from our collection.

Technology

Recognition Display Orientation Lock Configuration for School Touchscreens: A Configuration Checklist

Recognition display orientation lock configuration is the process of permanently fixing the screen rotation of a wall-of-fame kiosk, digital trophy case, or awards touchscreen so that the display stays in its intended portrait or landscape layout after every restart, OS update, and power cycle — without requiring a technician to manually correct the rotation.

Aug 16 · 20 min read
Technology

Recognition Display SNMP Monitoring for School IT Teams: Uptime, Temperature, and Alerting

Recognition display SNMP monitoring is the practice of querying your hall of fame kiosks, lobby touchscreens, and donor wall displays over the Simple Network Management Protocol — collecting uptime counters, interface statistics, CPU and memory utilization, disk capacity, and hardware temperature — and routing those metrics to a centralized alerting system before a device fails in front of an audience.

Aug 15 · 21 min read
Technology

Touchscreen Recognition Display Watchdog Timer Configuration: Recover from App and Device Freezes

Touchscreen recognition displays earn their keep during the events that matter most—championship ceremonies, hall of fame inductions, graduation weekends, and alumni homecomings. Those are also the moments when a frozen screen or crashed player draws the most attention and reflects most directly on the staff responsible for the installation. A blank kiosk in front of a crowd of parents and alumni is not a minor inconvenience; it is a visible failure during a high-stakes presentation.

Aug 14 · 19 min read
Technology

Touchscreen Recognition Display Touch-Latency Test: Measure Response Before Installation Sign-Off

A touchscreen recognition display that passes every network and power test can still fail its audience on the day of a hall of fame induction ceremony — not because the screen is dark or the content is missing, but because it feels sluggish. A visitor taps an athlete’s portrait and waits. They tap again. The panel responds half a second later to the first tap, then immediately to the second, now registering a double action. That half-second gap is touch latency: the time between a finger contacting the screen and the display registering the event in software. In a lobby kiosk or hallway recognition wall, perceived lag at that level is enough to make users stop interacting and walk away.

Aug 13 · 22 min read
Digital Signage

Digital Signage for Schools: Unlimited Screens, MDM Device Management, and $50/Year

Most schools approach digital signage procurement expecting per-screen monthly fees, separate content management licenses, and hardware contracts that push annual costs well into the thousands. A standard three-screen deployment across a gym lobby, main hallway, and front office commonly runs $2,400–$4,800 per year on subscription-based platforms—before adding design, support, or MDM management.

Aug 13 · 16 min read
Technology

Recognition Display Electrostatic Discharge Protection Checklist for School Installations

A school’s touchscreen recognition display can survive years of daily public interaction—fingerprints, casual bumps, humidity swings—and then fail silently because a technician grabbed the wrong edge of the controller board while swapping a USB cable. Electrostatic discharge is invisible, fast, and cumulative: a single discharge event may not destroy a component outright but can weaken it enough to cause intermittent failures weeks later during a championship ceremony or alumni induction event. In carpeted school hallways where students shuffle past lobby kiosks all day, static voltage buildup is a persistent and underestimated threat.

Aug 12 · 22 min read
Technology

Recognition Display EDID Troubleshooting Checklist for School AV Teams

A school’s touchscreen recognition display is working perfectly on Monday. By Friday—before the athletic banquet—it is showing a scrambled resolution, a black screen, or a “No Signal” message that no cable swap seems to fix. The source device is on. The display is powered. The HDMI cable looks fine. The culprit in most of these cases is not hardware failure: it is an EDID handshake breakdown that happened silently during a routine power cycle, a firmware update, an AV extender restart, or a switch port change.

Aug 11 · 25 min read
Technology

Touchscreen Recognition Display PoE Power Budget Checklist for Schools

A touchscreen recognition display rarely arrives alone. Cameras, occupancy sensors, access-control readers, media players, and wireless access points often travel with it—each one expecting a Power over Ethernet port, each one drawing watts from a switch that has a finite total budget. Schools that skip the PoE power budget calculation discover the problem at the worst possible moment: a camera drops offline the day of a championship ceremony, or a lobby sensor stops responding and the display blanks during an open house. Running the numbers beforehand costs under an hour and prevents all of it.

Aug 10 · 12 min read
Technology

Touchscreen Recognition Display IT Asset Inventory Policy: What Schools Should Track

A touchscreen recognition display is not a flat-screen TV bolted to a wall—it is a networked computer, a licensed software platform, a warranted hardware assembly, and a piece of ADA-regulated public infrastructure. Schools that treat it like a piece of furniture end up in predictable trouble: the vendor needs a serial number for a warranty claim and nobody can find it, a network port is reassigned because IT did not know the display depended on it, or a software subscription lapses silently because the purchasing contact left two years ago.

Aug 09 · 15 min read
Technology

Touchscreen Recognition Display DHCP Reservation Checklist for School Networks

A school’s recognition display reboots during an overnight firmware update and comes back up with a different IP address. Remote monitoring stops alerting. The IT ticket to re-add the display to the remote access tool sits in the queue for three days. A content update scheduled before the athlete-of-the-year ceremony never syncs because the CMS cannot reach the device at its expected address. The kiosk works perfectly in the lobby—it just isn’t reachable from anywhere that matters. The root cause in nearly every case like this is the same: the recognition display was assigned a dynamic lease rather than a DHCP reservation.

Aug 08 · 25 min read
Technology

Touchscreen Recognition Display Wireless Site Survey Checklist: Verify Coverage Before Installation

A school orders a touchscreen recognition display for the main lobby, the installer mounts it, IT connects it to the nearest guest Wi-Fi SSID, and it works fine during Tuesday afternoon setup. Then the hall of fame induction ceremony happens on Friday evening. Sixty guests arrive, all their phones associate to the same access point that the display is connected to, and the recognition display stalls mid-presentation while athletic portraits and highlight videos buffer endlessly. The hardware is fine. The CMS is fine. The wireless coverage at that exact location was never verified under realistic event conditions before the mount went into the wall.

Aug 07 · 26 min read
Technology

Touchscreen Recognition Display Network Capacity Planning Checklist for School IT

A touchscreen recognition display in a school lobby runs flawlessly during Tuesday afternoon setup—and then a Friday evening induction ceremony happens. Forty guests crowd the hallway, every phone tries to join the guest Wi-Fi, and the recognition display cycles through spinning-load indicators instead of the athletic portraits and highlight videos that justify its installation. The IT team gets a call mid-ceremony. The display hardware is fine; the network path to the CMS is saturated. Without a written bandwidth assessment and a tested infrastructure plan, every high-attendance event is a potential failure scenario for a display that was working perfectly the day before.

Aug 06 · 23 min read
Technology

Touchscreen Recognition Display Power Quality Monitoring Log: Track Voltage Events and Uptime

A touchscreen recognition display in a school lobby or trophy hallway runs continuously—through HVAC startup surges, kitchen equipment cycling, voltage dips during peak load periods, and the occasional outage that takes the whole wing dark. Each of these electrical events leaves a mark: an unplanned restart, a corrupted media cache, a content loop that freezes on the wrong frame. Facilities teams get a work order. IT gets a call. The athletic director gets a black screen during a donor tour. Without a record that connects the electrical event to the display’s behavior, every incident looks random and every fix is a guess.

Aug 05 · 20 min read
Technology

Touchscreen Recognition Display DNS Filtering Checklist: Safe Access Without Breaking Content

A school’s DNS filter does exactly what it is supposed to do when it blocks the recognition display’s CMS from loading: it enforces a deny-by-default policy and the display’s cloud platform is not on the allowlist. The result is a touchscreen kiosk in your lobby that shows a blank screen or an error page during an alumni event, an induction ceremony, or a donor tour. For school IT teams rolling out or tightening content filtering across a network that includes public-facing recognition hardware, the gap between a secure filter and a working display is almost always a missing set of documented allowlist entries.

Aug 04 · 16 min read
Technology

Touchscreen Recognition Display USB Device Control Policy for School IT

A touchscreen recognition display in a school trophy case or athletics hallway is a public-facing endpoint. It runs an operating system, connects to the building network, and—unless policy says otherwise—accepts whatever a visitor plugs into any exposed USB port. An open USB port on an unattended kiosk is a physical vulnerability: anyone who walks past can insert a storage device loaded with autorun malware, attempt a live-boot attack from a bootable drive, quietly copy locally cached content, or connect a USB-based hardware implant that persists between reboots. None of these threats require an internet connection or a sophisticated attacker.

Aug 03 · 19 min read
Technology

Touchscreen Recognition Display Endpoint Hardening Checklist for School IT Teams

A touchscreen recognition display in a school lobby is not a desktop computer, a classroom device, or a managed workstation. It sits in a high-traffic corridor, it is connected to the same building network that hosts student records and staff email, and it operates unattended for hours at a time with no IT staff in sight. Default out-of-box settings — open USB ports, broad outbound firewall rules, remote desktop enabled, administrator passwords unchanged from the vendor’s staging configuration — are tuned for rapid deployment, not sustained public operation in an educational environment. The same kiosk that scrolls athlete hall of fame profiles during a Friday playoff game is also an endpoint that can be physically prodded, network-probed, and targeted by opportunistic scripts scanning for open services.

Aug 02 · 22 min read
Technology

Touchscreen Recognition Display Time Synchronization Checklist: Keep Devices, Logs, and Scheduled Content Aligned

A touchscreen recognition display that fires scheduled content at the wrong time during a graduation ceremony, produces audit logs with timestamps that don’t align with your network records, or loses its CMS connection because its internal clock drifted past a certificate validity boundary doesn’t fail quietly — it fails in front of the students, families, donors, and alumni your school most wants to impress. Athletic directors schedule championship highlight reels to loop before home playoff games. Advancement staff activate donor recognition windows to coincide with capital campaign launches. Facilities teams rely on accurate timestamps when reviewing who changed what and when on a public-facing display. IT coordinators cannot diagnose a blank screen caused by clock skew if the device’s logs don’t align with the rest of the network.

Aug 01 · 25 min read
Technology

Touchscreen Recognition Display Data Flow Diagram: Map Content, Accounts, and Devices

When a student athlete’s record is added to your school’s recognition platform, that single entry triggers a chain of events: a content editor saves it in a cloud CMS, the platform validates the account permission, a media file moves from upload storage to a CDN, and seconds later the lobby touchscreen renders a polished profile card. Each handoff is a potential point of failure — or a point where personal data can be exposed without proper controls.

Jul 31 · 15 min read
Technology

Touchscreen Recognition Display Configuration Baseline Checklist for School IT

A recognition display that ships from a vendor with default administrator credentials, an open remote desktop port, and a publicly routed IP address is not configured for your school’s security posture—it is configured for a warehouse staging bench. Default settings simplify first-time setup; they do not reflect your district’s network segmentation rules, your IT department’s account policies, or your facilities team’s recovery requirements. Without a written document that records every approved setting layer by layer, any technician who touches the display—for a firmware update, a layout change, or a vendor service call—has no reference point for what “correct” looks like. The result is configuration drift: a display whose live settings gradually diverge from what was originally approved, with no record of when, how, or why.

Jul 29 · 22 min read
Technology

Touchscreen Recognition Display Vulnerability Management Policy for Schools

A publicly accessible touchscreen in your school’s lobby or athletic hallway is a network-connected device. It runs an operating system, communicates with a content management platform, and—in many installations—touches your school’s Wi-Fi, VLAN, or data integration layer. When a CVE is published for the OS your display runs, or when a security researcher discloses a vulnerability in a common CMS plugin your recognition platform uses, your district’s exposure doesn’t wait for your next scheduled patch window. Without a formal policy for identifying, classifying, and remediating those vulnerabilities, the gap between disclosure and remediation is measured by luck rather than process.

Jul 28 · 21 min read

1,000+ Installations - 50 States

Browse through our most recent halls of fame installations across various educational institutions