When a metal and a nonmetal exchange electrons to make a cation and an anion, respectively, they can form an ionic compound. The formula of an ionic compound indicates the kinds and number of ions. The number of anions and cations create a compound with an overall charge of zero; in other words, the positive and negative charges are balanced.

Generally, we know that ionic compounds are formed by reaction of metals and non metals and non metals form a covalent  or non ionic bonds.

IONIC COMPOUDS

NON IONIC COMPOUNDS

Explanation:

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a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.