The characteristics of two different types of reactions are shown below:
reaction a: electrons are gained by the atoms of an element.
reaction b: protons are lost by the atom of an element.
which statement is true about the atoms of the elements that participate in the two reactions?

Electrons are gained by the atoms of an element.  

Explanation:

Chemical reactions involve the electrons of an element. Of course, if one atom gains electrons, some other atom must lose them.

Reaction B is wrong. Protons are in the nucleus of an atom and do not take part in chemical reactions.

Reaction A is True

Explanation:

Electrons play a role in chemical reactions.

An atom is neutral and containing same number of positive protons and negative neutrons

Atomic number =number of electrons = number of protons

To find the number of neutrons we make use of the formula  

Mass number-atomic number = number of neutrons

Electrons are present around the nucleus. Protons and neutron are present inside the nucleus which is present in the center of the atom. Protons and neutrons are not involved in a chemical reaction.

Atoms either lose or gain or shares electron during a chemical reaction in order to attain stability and to arrive at the noble gas configuration.

Na loses one of its electron to form (Negative charge lost)

Cl gains one electron which the Na metal has lost to form (Negative charge gained)

The electrostatic force of attraction between and leads to the formation of NaCl compound.

there are no statements provided but here is why:

sulfur belongs to group 16 because it can be found in nature whether it is in a free or combined state.

hope this

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).