Let's start by defining compound and ion.
A compound is a substance formed when exactly two elements combine to form a new substance. The new compound formed is electrically neutral.
An ion is an atom, or group of atoms, that has electrical charge. This charge could be positive (when there is a shortage of electrons), or negative (when there is an excess of electron).
A binary compound consists of exactly two elements. Given below are the names and formulas of some binary compounds with the elements that combined to form them.
Compound Formula Elements
Water H2O hydrogen and oxygen
Carbon dioxide CO2 carbon and oxygen
Methane CH4 carbon and hydrogen
Ammonia NH3 nitrogen and hydrogen
Sodium chloride NaCl sodium and chlorine
A polyatomic ion is a group of atoms that are chemically bonded, and have a net charge on them. Some polyatomic ions are given below.
hydroxyl ion [OH]-
nitrate ion [NO3]-
sulfate ion [SO4]2-
Julie S.
Just to make a quick correction - a Compound is "two or more" elements chemically combined to form a new substance. Does not have to be exactly 2 elements. If it is 2 elements then the compound is a binary compound. If there are 3 different elements then it is a ternary compound (or some people just call it complex). Usually 4 or more elements we just call "complex" or don't categorize specifically.02/17/20