Use the periodic table to identify the number of core electrons and the number of valence electrons in each case below. Potassium (K) : 1s22s22p63s23p64s1

18 core electrons

1 valence electron

Explanation:

In the periodic table, potassium stands at the head or beginning of the fourth period. It is found in group 1. The third period ends with argon having 18 electrons. This implies that potassium should have at least 18 core electrons. Since it is found in group 1 having only 1 valence electron, it is expected to also have one valence electron.

Its electron configuration summarizes these statements above; 1s22s22p63s23p64s1

There are 18 core electrons and one valence electron in the outermost 4s1 orbital (the fourth shell)

The number of core electrons = 18 electrons.

The number of valence electrons = 1 electron.

Explanation:

The core electrons are the electrons in the inner shells (1s²2s²2p⁶3s²3p⁶).

∴ the number of core electrons = 18 electrons.

The valence electrons are the electrons in the outermost shell (4s¹).

∴ the number of valence electrons = 1 electron.