Question

The electron configuration for an atom is 1s 2s 2p2. How many electrons does the atom have?

2
4
5
6

Answer 1

Four

Step-by-step explanation:

The superscripts in an electron configuration tell us how many electrons are in a subshell.

If the electron configuration is 1s¹ 2s¹2p², the total number of electrons is

1 + 1 + 2 = 4

The atom contains four electrons.

Note: this atom is in an excited state, because the 1s and 2s subshells can each hold one more electron.