Question

The electron configuration of an element is 1s^22s^1. How many valence electrons does the element have?

Answer 1

The answer Would be two

Answer 2

Answer : The number of valence electron present in an element is, 1

Explanation :

Electronic configuration : It is defined as the representation of electrons around the nucleus of an atom.  

Number of electrons in an atom are determined by the electronic configuration.

Atomic number : It is defined as the number of electrons or number of protons present in a neutral atom.

The given electronic configuration of an element is,

$1s^22s^1$

That means, the element has 1 valence electrons.