Question

What is the formula when the halogen from 3rd principal energy level combines with you alkaline earth metal from the 4th energy level?

Answer 1

Answer: $CaCl_2$

Explanation:

Principle Quantum Numbers : It describes the size of the orbital and the energy level. It is represented by n. Where, n = 1,2,3,4....

Halogen with n=3 is chlorine.

Alkaline earth metal with n = 4 is calcium.

An ionic bond is formed when an element completely transfers its valence electron to another element.

Electronic configuration of calcium

$[Ca]=1s^22s^22p^63s^23p^64s^2$

calcium atom will loose one electron to gain noble gas configuration and form calcium cation with +2 charge.

$[Ca^{2+}]=1s^22s^22p^63s^23p^6$

Electronic configuration of chlorine:

$[Cl]=1s^22s^22p^63s^23p^5$

Chlorine atom will gain one electron to gain noble gas configuration and form chloride ion with -1 charge.

$[Cl^-]=1s^22s^22p^63s^23p^6$

Here $Ca^{2+}$ cation and chloride $Cl^{-}$ anion combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral $CaCl_2$.