Worth 20 explain how to use valence electrons to predict if an atom will form bonds.

Valence electrons predict the formation of bonds based on how MANY electrons are placed on the elements outer shell.

Initially, all elements want an outer valence electron shell of 8 electrons. This is called the Octet Rule.
Here’s the key part: In order to gain those 8 valence electrons there must either be a LOSS or a GAIN in electrons. The elements that give give up their electrons are metals, while nonmetals gain the electrons that metals offer to them. This way, they’re able to form a bond together that makes them “wholesome.” (FULL 8 electron outer shell)

It’s important to keep in mind the families of the periodic table; alkali metals, alkaline earth metals, transition metals, halogens, etc,...

For example:
Oxygen is a nonmetal and has a valence electron shell of six, therefore it will want to gain two of its valence electrons to make a full outer shell.

In order to make a wholesome bond, oxygen MUST bond with an element in the Alkaline Earth Metal family in order to be whole since Alkaline Earth Metals have a valence electron outer shell of two. Being a metal, they will want to give away their two valence electrons.
Let’s just say that oxygen decided to pair with beryllium.

Therefore the bond would be;

BeO

A.(nh4)(2co3)is the correct answer