What is calcium used for in our body?

It is necessary for contracting muscles, forming and strengthening bones and teeth, conducting nerve impulses throughout the body, clotting blood, maintaining a normal heartbeat

calcium is essential for living organisms.  it is vital for the body's good health.

Bone health

Vitamin D is helps the body absorb and retain calcium

it helps with muscle contraction

helps in normal blood coagulation (clotting)

it is a co-factor for many enzymes

helps the smooth muscles that surrounds the blood vessels; causes it to relax

Explanation:

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.