# Question #035a0

Apr 17, 2016

I think the clue to both of these understanding the meaning of the first word.

#### Explanation:

Taking each question in turn: " hydrate, compound, water "

A hydrate is a substance formed by combination of a compound with water. In inorganic chemistry, these are usually ionic salts with water molecules loosely attached.

An example of the formula of such a substance is : $M g S {O}_{4.} {\left({H}_{20}\right)}_{7}$ (this is 7 loosely bound water molecules around the magnesium and sulphate ions).

"A hydrate is a substance formed by the combination of a compound with water, often involving ionic salts with water molecules loosely attached".

Looking at the next question: " oxidation number, element, electrons "

The oxidation number of an atom is the number of electrons that an atom can lose, gain or share when chemically bonding with another element.

For example, in NaCl, the oxidation number of Na is +1 (it loses one electron when bonding), and the oxidation number of Cl is -1 (it gains one electron when bonding).