Two elements in the second transition series (y through
cd)have four unpaired electrons in their 3+ ions. what elements
fitthis description?

Technetium and Rhodium

Explanation:

For Technetium, Symbol: Tc

Atomic number: 43

Electron configuration: [Kr] 4d55s2

Atomic mass: 98 u

For Rhodium, Symbol: Rh

Electron configuration: [Kr] 4d85s1

Atomic number: 45

Atomic mass: 102.9055 u

Technetium (Tc) and Rhodium (Rh)

Explanation:

The two elements in the second transition series ( Y through Cd) that have four unpaired electrons in their 3⁺ ions are

Tc [Kr] 4d⁵5s²  after losing 3 electron becomes Tc [Kr] 4d⁴ and

Rh [Kr] 4d⁸ 5s¹ after losing 3 electron becomes Rh [Kr] 4d⁶  where Kr is the electronic configuration of Krypton ( a noble gas)

so both  Technetium (Tc) and Rhodium (Rh) have four unpaired electrons

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.