compounds and formulae

Question 1

what are compounds?

Answer 1

a substance of chemically bonded non-metals or a non-metal and metal atom

Question 2

what is the formula of methane?

Answer 2

ch4

Question 3

how do you work out the formula of ionic compounds using the charges on ions?

Answer 3

by using the principle that the total positive charge must equal the total negative charge
eg formula for magnesium chloride:
magnesium = mg2+, chloride = cl-
.'. 2 chlorides needed for 1 magnesium
mgcl2