How many valence electrons does the element have if the electron configuration is 1s2 2s2

2 valence electrons

Explanation:

Data Given

Electronic Configuration = 1s², 2s²

valence electrons = ?

Solution:

An atom of element have orbitals, and electrons are revolving in it.

There are quantum numbers that describe the number of electron in specific shell.

The Principle quantum number is denoted by "n" and can not be "0".

These n is K, L, M, N and electrons are distribution in it.

K =2

L= 8

M= 18

According to Aufbau electron occupied in the lowest energy level before occupying the highest energy level.

According to this the electronic configuration is

1s², 2s², 2p⁶ and so on

The 1st orbital is 1s and it only can occupy 2 electrons the next coming electron goes into 2s that also can occupy 2 electrons and the further electrons will go to 2p orbital.

So,

From this explanation we come to know that this element only have 4 electrons.

from these 4 electrons 2 will go to 1s and other 2 will goes to 2s orbitals.

So, the valance electrons are 2

this configuration is of Be that have 4 electrons as it have valency of 2+.