Answer:
The unit that is a radical among the options is;
a. NH₄⁺
Explanation:
A radical is an atom, group of atoms molecule or ion that contains an electron that is unpaired. The presence of the unpaired electrons make radical very reactive as such most radicals enter into reactions with other species or with themselves to form new compounds making them not last long.
Radicals are also known as free radicals. Examples of radicals includes; Ammonium ion, NH₄⁺
Nitrate ion NO₃⁻ (From a salt)
Hydroxide ion OH⁻ (From a base)
Sulphate ion SO₄²⁺ (From an acid)
All of which are formed in aqueous solution of acids, salts and bases.
A. freezing, when water turns to ice the water is turning from a liquid to a solid.
