Answer: Formation of a stable Duplet or Octet structure
Explanation:
Energy levels refers to the definite amount of energies that electrons can have when occupying specific orbitals.
Examples are:
Level 1 as in 1s
Level 2 as in 2s, 2p
Level 3 as in 3s 3p 3d
Level 4 as in 4s 4p 4d 4f
Level 5 as in 5s .......
Level 6 as in 6s .........
Electrons can be excited to higher energy levels by absorbing energy from the surroundings during chemical reactions and so forming chemical bonds like ionic, covalent etc.
A perfect example is Sodium (Na) and Chlorine (Cl) in Sodium chloride (NaCl)
Sodium has atomic number of 11, so energy level is 1s2, 2s2 2p6, 3s1
Chlorine has atomic number of 17, so energy level is 1s2, 2s2 2p6, 3s2 3p5
You will notice that the both Na and Cl, has electrons in the energy level 3. Then, the bond formed must be one that lead to the formation of a OCTET structure: as in Na gives off its 3s1 electron TO Cl.
Thus, Cl now becomes 1s2, 2s2 2p6, 3s2 3p6 - an OCTET STRUCTURE (with completely filled outershell and full energy level 3) in NACl.
So, a duplet or Octet structure is the answer
