5.3.1: Transition metals

Question 1

What is a transition element (transition metal)

Answer 1

A d-block element that has an incomplete d-sub-shell as a stable ion.

Question 2

Why are scandium and zinc, the first and last members of the Period 4 d-block elements, not classified as transition metals?

Answer 2

• They do not have any ions with partially filled d-orbitals.
• Scandium forms only the Sc3+ ion, in which the d-orbitals are empty.
• Zinc forms only the Zn2+ ion, in which the d-orbitals are full.

Question 3

Why do the 4s-orbitals fill before the orbitals in the 3d-sub shell?

Answer 3

-Because the 4s-sub shell has a lower energy than the 3d-sub-shell.

Question 4

How are the electron configuration of chromium and copper different (doesn’t follow the pattern of filling the lowest energy levels first)?

Answer 4

Chromium:
-The five 3d-orbitals and the 4s-orbitals all contain one electron, with no orbital being completely filled.
-The 4s orbital and the 3d-orbitals are half filled.
Copper:
-The five 3d-orbitals are full, but there is only one electron in the 4s-orbital.
-The five 3d orbitals are filled and the 4s-orbital is half filled.

Question 5

Why is it better for chromium and copper to not follow the regular pattern?

Answer 5

-In these two elements, the electron repulsion between the outer electrons are minimised, resulting in increased stability of the chromium and copper atoms

Question 6

Transition metals lose electrons in reactions to form positive ions. Which sub shell loses electrons first and why?

Answer 6

-Transition metals lose their 4s electrons before their 3d electrons.
-The 3d and 4s energy levels are very close together and, once electrons occupy the orbitals, the 4s electrons have a higher energy and are lost first.
(NB: gained first in 4s, lost first)