Question

A chemical species that contains 10 electrons and 10 protons can be:

• A. An atom
• B. A molecule
• C. An anion
• D. A cation

Answer 1

Answer: (A), (B)

A molecule

Explanation for correct options:

(A) An atom: It is defined as the smallest constituent of matter that defines the properties of a chemical element. According to Thomson's model of atom “ atom as a whole is electrically neutral” which means that in an atom the number of electrons is equal to the number of protons.

(B) A molecule: It is formed when two or more atoms are chemically bonded to each other forming a molecule. For example; when two oxygen atoms combine they form ${\mathrm{O}}_2$ molecules. Molecules are neutral in nature i.e. they contain an equal number of electrons ad protons.

Explanation for incorrect options:

(C) An anion: It is defined as a negatively charged ion that is formed when an atom gains electrons to complete its octet and become stable. Since the ion formed is having more electrons than protons, hence carries a net positive charge and is not neutral. An example of anion is ${\mathrm{Cl}}^{-},{\mathrm{Br}}^{-}$etc.

(D) A cation: It is defined as a positively charged ion that is formed when an atom loses its electron (usually valence electron). Since the ion formed is having more protons than electrons, hence carries a net positive charge. An example of cation is etc.

Thus, options (A) and (B) are correct because a chemical species that contains 10 electrons and 10 protons can be either an atom or a molecule.