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@media(max-width:850px){.brand{font-size:17px}.brand svg{width:32px;height:32px}.brand small{font-size:6px}.header-inner{flex-wrap:wrap;gap:14px;min-height:80px}.primary{gap:15px;font-size:12px}.search-wrap{width:100%;order:3}.hero{padding-top:36px;gap:25px}.hero-copy h1{font-size:47px;letter-spacing:-2.5px}.hero-copy>p:not(.eyebrow){font-size:14px}.hero-actions{gap:16px;align-items:flex-start;flex-direction:column}.hero-facts{gap:12px;flex-wrap:wrap}.hero-facts span{font-size:9px}.hero-facts span+span{padding-left:12px}.feature-element{padding:22px;min-height:320px}.feature-top{font-size:7px;letter-spacing:1px}.feature-caption{font-size:6px}.atom-art{width:230px}.learn-section{grid-template-columns:1fr 1fr}.learn-section>div{grid-column:1/-1;display:block}.learn-section>div p:not(.eyebrow){max-width:500px}.learn-section h2 br{display:none}.faq-section{gap:30px}.faq-section h2{font-size:27px}.footer-top{grid-template-columns:1fr 1fr;gap:35px}.footer-brand{grid-column:1/-1}footer{padding:35px 26px 20px}.element-layout{grid-template-columns:210px 1fr;gap:25px}.property-grid{grid-template-columns:1fr}.panel-symbol{font-size:90px}.page-heading{padding-top:32px}}
@media(max-width:600px){html{scroll-padding-top:145px}.header-inner{padding:15px 18px;gap:12px}.brand{font-size:15px;gap:8px}.brand small{font-size:5.5px;letter-spacing:1.2px}.brand svg{width:30px}.primary{font-size:10px;gap:12px}.primary a:last-child{display:none}.search-wrap{padding:9px 12px}.search-wrap input{font-size:13px}main{padding:0 18px}.hero{display:block;padding:32px 0 30px}.eyebrow{font-size:8px;letter-spacing:1.8px}.hero-copy h1{font-size:54px;letter-spacing:-3px;margin:18px 0}.hero-copy h1 span{letter-spacing:-2.5px}.hero-copy>p:not(.eyebrow){font-size:14px;max-width:340px}.hero-actions{flex-direction:row;align-items:center;gap:22px;margin-top:24px}.button{font-size:11px;padding:12px 16px;gap:17px}.text-link{font-size:11px}.hero-facts{margin-top:25px;gap:15px}.hero-facts span+span{padding-left:15px}.hero-facts b{font-size:21px}.feature-element{margin-top:28px;min-height:205px;padding:19px 22px}.feature-top{font-size:7px}.feature-symbol{font-size:70px;margin-top:20px}.feature-symbol small{font-size:9px;margin-left:3px}.feature-bottom{position:absolute;left:115px;right:22px;bottom:55px;gap:10px}.feature-bottom h2{font-size:22px}.feature-bottom p{font-size:10px}.feature-caption{position:absolute;bottom:16px;left:22px;right:22px;margin:0;padding-top:10px}.atom-art{width:205px;height:205px;right:-22px;top:0;opacity:.7}.round-arrow{width:31px;height:31px;font-size:17px}.table-section{padding-top:26px}.section-head{margin-bottom:20px}.section-head h2{font-size:26px}.filters{gap:10px;align-items:flex-start;flex-wrap:wrap}.filter-buttons{gap:0}.filters button{padding:7px 10px;font-size:10px}.view-buttons{margin-left:auto}.mobile-hint{display:block;font-size:10px;color:var(--muted);margin:0 0 12px}.periodic-grid{grid-template-columns:20px repeat(18,54px);grid-template-rows:20px repeat(7,76px) 18px repeat(2,76px);min-width:1060px}.legend{gap:8px 14px;padding-top:15px}.legend button{font-size:9px}.learn-section{padding:30px 0;gap:12px;margin-top:10px}.learn-section>div{padding:0}.learn-section h2{font-size:28px;max-width:300px}.learning-card{padding:18px 15px}.learning-card>span{font-size:7px;letter-spacing:.8px}.learning-card h3{font-size:22px;margin-top:30px}.learning-card p{font-size:11px}.learning-card b{font-size:9px}.family-links{grid-template-columns:1fr 1fr}.family-link{padding:15px 9px;font-size:9px;gap:6px}.families-section{padding:25px 0 35px}.families-section .section-head{align-items:start}.families-section .text-link{font-size:10px;max-width:90px}.faq-section{display:block;padding:30px 0 40px}.faq-section h2{font-size:27px}.faq-section>div:first-child{margin-bottom:15px}.faq-section h2 br{display:none}summary{font-size:12px;padding:18px 22px 18px 0}.footer-top{gap:25px}.footer-brand{font-size:28px}footer{padding:30px 18px 20px}.footer-bottom{gap:20px;font-size:8px}.breadcrumbs{font-size:9px;padding-top:20px;gap:8px}.page-heading{padding:28px 0 20px}.page-heading h1{font-size:39px;letter-spacing:-1.7px}.page-heading .lead{font-size:14px}.element-layout{display:block}.element-panel{position:relative;top:0;display:grid;grid-template-columns:1fr 1fr;padding:20px;text-align:left;margin:0 0 30px}.panel-number{grid-column:1;grid-row:1}.panel-symbol{grid-column:1;grid-row:2/5;font-size:80px;line-height:1.4}.element-panel h2{grid-column:2;grid-row:2;align-self:end;font-size:24px}.element-panel>p{grid-column:2;grid-row:3;margin:0 0 10px;font-size:11px}.family-pill{grid-column:2;grid-row:4;font-size:9px;padding:5px 9px;justify-self:start;align-self:start}.panel-bottom{grid-column:1/-1;margin-top:12px;padding-top:12px;text-align:center}.panel-bottom b{display:inline;margin-left:10px;font-size:14px}.property-grid{grid-template-columns:1fr 1fr}.property-grid>div{padding:13px}.property-grid dd{font-size:13px}.property-grid dt{font-size:9px}.element-content h2{font-size:23px}.element-list{grid-template-columns:repeat(auto-fill,minmax(85px,1fr));gap:8px}.element-list .element{min-height:112px}.element-list .element>strong{font-size:30px}.element-list .element-name{font-size:10px}.prevnext{font-size:10px;gap:10px}.prose-section{padding:25px 0}.prose{font-size:13px}.family-links.large{grid-template-columns:1fr}.large .family-link{font-size:14px;padding:20px}.downloads{grid-template-columns:1fr;gap:16px}.download-card{padding:25px}.download-card h2{margin-top:35px;font-size:27px}.notice{padding:16px;font-size:11px}.table-scroll.list-view .periodic-grid{grid-template-columns:repeat(auto-fill,minmax(85px,1fr))}.list-view .element-name{font-size:10px}.list-view .element{min-height:110px}.table-scroll{margin-right:-18px;padding-right:18px}.table-scroll.list-view{margin:0;padding-right:0}.guide h2{font-size:24px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*:before,*:after{transition:none!important;animation:none!important}}
@media print{header,.hero,.filters,.legend,.learn-section,.families-section,.faq-section,footer,.breadcrumbs,.prevnext,.source-note,.mobile-hint,.reset-filters{display:none}body{background:white}main{padding:0;max-width:none}.periodic-grid{min-width:0;grid-template-columns:20px repeat(18,1fr);grid-template-rows:15px repeat(7,55px) 10px repeat(2,55px);gap:2px}.element{break-inside:avoid;print-color-adjust:exact}.element>strong{font-size:17px}.element-name{font-size:6px}.atomic-mass{font-size:5px}.table-note strong{font-size:14px}.table-note .eyebrow,.table-note a{display:none}.element-panel{position:static}.table-scroll{overflow:visible}.element.dimmed{opacity:1}}
.inline-arrow{display:inline-block;width:.85em;height:.85em;fill:none;stroke:currentColor;stroke-width:1.35;vertical-align:baseline;flex-shrink:0}.round-arrow .inline-arrow{width:14px;height:14px}.brand-light{margin-left:3px}
canvas.atom-art{pointer-events:none}
/* A little room around the grid keeps enlarged edge tiles inside the scroll area. */
@media screen {
 .periodic-grid{padding:30px 24px}
 .periodic-grid .element{transition:transform .22s ease,box-shadow .22s ease,opacity .2s;transform-origin:center}
 .periodic-grid .element:focus-visible{transform:scale(1.75);z-index:3;box-shadow:0 8px 22px #17374630}
}
@media screen and (hover:hover) and (pointer:fine){
 .periodic-grid .element:hover{transform:scale(1.75);z-index:3;box-shadow:0 8px 22px #17374630}
}
@media (prefers-reduced-motion:reduce){
 .periodic-grid .element{transition:none}
}

/* Cover illustrations for the eight existing element pages (111–118). */
.element-cover{margin:0 0 38px}.element-cover picture{display:block;overflow:hidden;border-radius:18px;background:#eaf0ee;aspect-ratio:3/2}.element-cover img{display:block;width:100%;height:auto}.element-cover figcaption{font-size:11px;line-height:1.7;color:var(--muted);margin-top:12px}
@media(max-width:600px){.element-cover{margin-bottom:28px}.element-cover picture{border-radius:12px}.element-cover figcaption{font-size:10px}}