Which is the best description of a molecule?
a molecule of an element is composed of at least two types of atoms.
o amolecule of a compound is composed of only one type of atom.
o amolecule of a compound is composed of at least two types of atoms.
a molecule of an element is composed of exactly two types of atoms.

A molecule of a compound is composed of at least two types of atoms.

Explanation:

A molecule is defined as when two or more atoms of an element combine together by the bonds by sharing the electrons as O^2 (oxygen molecule)

A compound is a molecule when two different types of atom joined by chemical bonds as covalent, ionic or coordinate bonds as NH^3 ( ammonia)

the dissociation of nickel hydroxide is follows:

the concentration of hydroxide ion is

the equilibrium constant value of nickel hydroxide is = 6.1 * 10^-^1^6 and thus equilibrium equation can be written as:

thus, concentration of ni is 0.23 * 10^-^4 mol /l