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.
and closing
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The heart has 4 valves. They are what makes the lub-dub lub-dub sounds that can be heard from the chest.
The mitral valve is located between the left atrium and the left ventricle. It closes the left atrium to collect oxygenated blood from the lungs and opens to pass it on to the left ventricle.
The tricuspid valve is located between the right atrium and the right ventricle. It closes the right atrium to hold unoxygenated blood and opens to pass it on to the right ventricle ensuring a one way flow.
The aortic valve is located between the aorta and the left ventricle. It closes the left ventricle and opens to the aorta to pass on the oxygen-rich blood to the body.
The pulmonary valve is located between the pulmonary artery and the right ventricle. It closes off the right ventricle and opens to pass on unoxygenated blood to the lungs.
The presence of mass makes gravity. Doesn't matter whether it's a planet, a black hole, a puppy, or a speck of dust.
