.nclr {
display: inline-block;
position: relative;
vertical-align: middle;
text-align: center;
margin: 0 2px;
}

.nclr > span {
display:block;
}

.nclr span.nucleons {
text-align: right;
font-size: 0.8em;
}

.nclr span.atomic {
text-align: right;
font-size: 0.8em;
}