Question

Here is the electron configuration for Argon. What does the coefficient 3 in 3s2 tell us?

Answer 1

The coefficient 3 represents the electron shell

Further explanation  

In an atom there are levels of energy in the shell and sub shell  

This energy level is expressed in the form of electron configurations.  

Writing electron configurations starts from the lowest to the highest sub-shell energy level. There are 4 sub-shells in the shell of an atom, namely s, p, d and f. The maximum number of electrons for each sub shell is  

• s: 2 electrons  

• p: 6 electrons  

• d: 10 electrons and  

• f: 14 electrons  

Charging electrons in the sub shell uses the following sequence:  

1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁶, 5s², 4d¹⁰, 5p⁶, 6s², etc.  

Argon is a noble gas element with the symbol Ar with atomic number 18 and mass number 40

Electron configuration: [Ne] 3s²3p⁶

The coefficient 3 represents the electron shell, which is denoted as the quantum number n

This shell consists of 3 sub shells namely 3s, 3p and 3d which have a maximum of 18 electrons (3s = 2 electrons, 3p = 6 electrons and 3d = 10 electrons)