Answer:
Argon
Explanation:
The arrangement of electrons in an atom is governed by the Aufbau principle according to which electrons are added to atomic orbitals such that the lowest energy orbitals get occupied first before the higher energy orbitals. The arrangement of energy levels in increasing energy order is:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p......
's' , 'p', 'd' orbitals can accommodate a maximum of 2,6 and 10 electrons respectively.
From the given information:
First energy level corresponds to n = 1, and is fully filled i.e. 1s²
Second energy level corresponds to n = 2, and is fully filled i.e. 2s²2p⁶
Third energy level corresponds to n = 3 and it has 8 electrons i.e. 3s²3p⁶
The neutral atom has a total of 18 electrons with an electronic configuration of:
1s²2s²2p⁶3s²3p⁶
Based on the periodic table the atom is with atomic number = 18 is argon (Ar)
