Group 3: the scandium group

Three electrons beyond the noble gas core

Scandium is [Ar] 3d¹ 4s² and yttrium is [Kr] 4d¹ 5s²: two s electrons and one d electron sit outside a noble gas core. Losing all three is easy, so the only common ions are Sc³⁺ and Y³⁺, found in oxides such as Sc₂O₃ and Y₂O₃.

Once those three electrons are gone, no d electrons are left, so most of their compounds are white or colorless, unlike the bright compounds of many transition metals. Both elements also behave much like the lanthanides, which prefer a 3+ charge too.

Scandium and yttrium compared

With only two full members, the trend is short. Yttrium is denser, 4.469 g/cm³ against 2.989 g/cm³ for scandium, and its electronegativity is lower, 1.22 versus 1.36. Their melting points are almost equal: 1814 K for scandium and 1799 K for yttrium. Scandium is light for a transition metal, only a little denser than aluminum (2.7 g/cm³).

Where you meet group 3

A little scandium strengthens aluminum alloys for bicycle frames, baseball bats and aircraft parts, and scandium iodide gives some stadium lamps a daylight-like glow. Yttrium aluminum garnet is the crystal in many lasers and in the phosphor that turns blue LED light white, and a yttrium barium copper oxide was the first superconductor to work when cooled with liquid nitrogen.

With the lanthanides, scandium and yttrium count as rare earth elements. Yttrium is named after Ytterby, a Swedish village that also gave its name to ytterbium, terbium and erbium.

What goes below yttrium?

Chemists still argue about which elements complete group 3. Many textbooks put lanthanum (57) and actinium (89) under yttrium, while many chemists now prefer lutetium (71) and lawrencium (103), because several properties then continue the scandium–yttrium trend more smoothly. This site keeps both series in their own rows, and the group 3 column shows a placeholder for each.