Ionic and covalent substances?

Question

How do you work out if a substance is ionic or covalent?

Answer 1

The main way to determine this is to find out whether the substance contains ions (for an ionic substance) or simple molecules or a giant molecule (for a covalent substance).

As has been said, generally if the substance is formed from a metal and a non-metal the substance will be ionic e.g. sodium chloride.  By giant molecule I mean something like diamond (Carbon) which contains just carbon atoms and forms one giant molecule (macromolecule).

A substance formed between a non-metal and another non-metal e.g. ammonia NH3 is generally covalently bonded.

However at A-level standard you learn that the above generalizations do not always give the correct answer

e.g. some ionic substances have a degree of covalent character and some covalent substances have some degree of ionic character.

Answer 2

If the difference between the electronegativities of the bonded atoms is greater than 1.7, the bond is ionic. If less than 1.7, the bond is covalent

Answer 3

A metal-nonmetal bond is usually ionic.

Answer 4

an ionic substances is usually react between a metal and a non-metal...

an covalent substances is usually react between a non-metal and a non-metal...

Answer 5

you look at the properties the substance has

e.g NaCl - soluble and conducts electricity when dissolved in water so must be ionic

covalent substances dont conduct electricity

also you can look at the structures they have

Answer 6

Ionic bonds are formed when metallic elements lose their valence electrons to nonmetal atoms that gain them.  The metal atoms become + ions, the nonmetal atoms become - ions and the oppositely charged ions attract to form the ionic bond.  Substances formed by ionic bonding are called ionic substances, and they generally have high melting points and conduct electricity in the liquid phase and when dissolved in water (electrolytes).

Covalent bonds are formed from nonmetal atoms that both have high electronegativity.  Instead of losing or gaining electrons, the nonmetal atoms share their unpaired valence electrons to form "shared pairs" that will give each bonded atom a total of 8 valence electrons (a stable octet).  The exception to this is hydrogen, which has only one energy level, and therefore will have only two electrons, both shared with the bonded atom.  Covalent bonds form particles called molecules, which generally have low melting points, and are poor conductors of electricity in all phases.

Electronegativity difference can be used to determine the ionic character of a bond.  he greater the END, the greater the ionic character.  The lower the END, the greater the covalent character.  The average END cutoff between ionic and covalent is 1.7, but that is not hard and fast.

Answer 7

Typically, a metal-non metal compound is ionic. ex, NaCl. While a non-metal-non metal compound is covalent.

To determine the type of bonds, the electro negativity of the elements can be used. If the difference between the two elements is small (can't remember the exact value), then the bond is covalent. The bigger the difference, the more ionic the bond.