According to the law of conservation of matter, the number of is not changed by a chemical reaction.

Answer ;

atoms

Explanation ;

The law of conservation of matter states that atoms cannot be created or destroyed by chemical reactions. Therefore, the number of atoms is not changed by a chemical reaction. However, the way the atoms are combined is changed, so the number of bonds, molecules, and products can all change.

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.