Question

Both Ti and Hf behave as though they possess the same number of valence electrons. Which of the subshells in the electron configuration of Hf behave as valence orbitals?

1s
2s
2p
3s
3p
4s
3d
4p
5s
4d
5p
6s
4f
5d

Answer 1

Do the electron configuration of both atoms.

Ti:

Atomic number 22.

Abbreviated electron configuration: [Ar] 3d^2 4s^2

Valence electrons 4s^2

Hf:

Atomic number: 72

Abbreviated electron configuration: [Xe] 4f^14 5d^2  6s^2

The subshells that behave as valence orbitals are, generally, those of the highest energy level.

In this case those are 6s.

Answer: 6s

Answer 2

Answer: The sub shells which behave as valence orbitals are '5d' and '6s'.

Explanation:

Valence orbitals are defined as the outermost orbitals from which an atom looses or gains electrons to attain stability.

Metals are defined as the elements which loose electrons to attain stability.

Non-metals are defined as the elements which gain electrons to attain stability.

Hafnium is the 72th element of the periodic table having electronic configuration of $[Xe]6s^24d^{10}5d^{2}$

This element is a transition element and shows variable oxidation of +2 and +4.

Thus, hafnium may loose electrons from either '6s' subshell of from '5d' subshell.

Hence, the sub shells which behave as valence orbitals are '5d' and '6s'.