An atom has the following electron configuration.

1s22s22p63s23p64s23d3

How many valence electrons does this atom have?

A. 2

B. 3

C. 5

D. 11

Answer: 5

Explanation: add up all the electrons and it will amount to 23. Arranging by the old model for electronic configuration, we have : 2, 8, 8, 5

The last number being 5 represent its valence electron

vanadium has 5 valence electrons

Explanation:

The element with electron configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d3

has 23 electrons. This element is Vanadium.

For Vanadium, the atomic number is 23 and the electronic configuration given is

1s2 2s2 2p6 3s2 3p6 4s2 3d3

Vanadium's ground state electron configuration is [Ar] 3d3 4s2.

Thus vanadium has 5 valence electrons and during ionic bonding, s-shell electrons are lost first and than d-shell electrons would be lost.