Question

Answer the following question in detail.

Define the following terms:

a) Atom

b) Molecules

c) Radical

d) Valency

Answer 1

a) Atom:

• It is the smallest particle of elements that exhibits all properties of an element and takes part in a chemical reaction. It may or may not have an independent existence.
• Atom is made up of protons, neutrons, and electrons.
• Atoms of the same element are identical but atoms of a different element are different. For example, Nitrogen is made up of nitrogen atoms while Oxygen is made up of oxygen atoms.

b) Molecule:

• A molecule is the smallest particle of an element or compound capable of independent existence and is formed by the combination of one or more than one atoms of the same or different type.
• Those molecules which are made up of some kind of atoms are known as molecules of an element. For example, the hydrogen molecule (${\mathrm{H}}_2$) is made up of only hydrogen atoms.
• Those molecules which are made up of different kinds of atoms are known as molecules of a compound. For example, the water (${\mathrm{H}}_2\mathrm{O}$) molecule is made of hydrogen and oxygen atoms.

c) Radical:

• It is an atom of an element or a group of an atom of different elements that behaves as a single unit with a positive or negative charge on it.

Radicals can be of two types:

• Basic radical: positively charged ion also known as a cation. Example, NH4+ (ammonium ion).
• Acidic radical: negatively charged ion also known as anions. For example, Cl-(chloride ion).

d) Valency:

• It is the combining tendency of an element or radical.
• Valency can be positive or negative or but never a fraction it is always a whole number.