please explain the EOS formula and also solve and explain the following problem

calculate the formal charge of phosphorous and oxygen atoms in PHOSPHORUS TETRAOXIDE (3-) ION

Dear student,

A.  Covalent bonds

 1.   are formed by sharing pair of electrons between two atoms. They are found in a long list of substances such as paper, garbage bags, sugar, bloodstream, DNA, and every tissue in the human body.

2.   Molecular substance is a substance that has atoms held together by covalent bonds

3.   A molecule may contain as many as few as 2 atoms or as many as thousand or even a million atoms. Examples:

Oxygen, a gas that travels through your bloodstream,

Hydrogen is a colorless, odorless gas that accounts for 75 percent of the universe's mass. It's also used in NASA's space program as fuel for the space shuttles, and in fuel cells that provide heat, electricity and drinking water for astronauts.

Nitrogen gas makes up about 78% of the atmosphere by volume

Commercially, CO₂ finds uses as a refrigerant (dry ice is solid CO₂), in beverage carbonation, and in fire extinguishers.

      E. Larger molecules such as DNA and polyethylene