Ionic and Covalent Compounds

Ionic and Covalent Compounds


What is an ionic compound?

• It is a chemical compound in which ions are held together by ionic bonds forming a lattice structure.
• It is comprised of a cation (usually metal or it can be a positively charged polyatomic ion) and an anion (usually a negatively charged polyatomic ion).
• It is a very hard and brittle subtsance with a high boiling and melting point.
• It is held together by electrostatic force.

How do you name an ionic compound?

1. Write the name of the cation first.
2. If applicable, write the charge of the cation with roman numerals if it mulivalent.
3. Write the name of the anion with either its polyatomic name or by changing the last syllable of the element to ide.

Examples:

HgClO -------> Mercury(l) hypochlorite

NH4H --------> ammonium hydride

CaSO4 --------> calcium sulphate


How do you write an ionic formula:

1. Write the cation's element/polyatomic ion symbol.
2. Write the anion's element/ polyatomic ion symbol.
3. Write and cancel out the charges as a subscript.

Examples:

Radium chlorite ----------> Ra(ClO2)2

Potassium fluoride -------> KF


What is a covalent compound?

• It is a chemical compound involving the sharing of electrons between atoms.
• It is always formed between two non-metals.
• It is usually has low melting and boiling points.
• It is usually soft and sticky.

How do you name a covalent compound?

1. Write the first element's name corresponding to its symbol
2. Write the second element's name corresponding to its symbol.
3. Write in prefixes to show the number of atoms.

Note: Elements hydrogen, oxygen, fluorine, chlorine and bromine all require the prefix mono if listed second in chemical formula.

Examples:

SF3 ----> sulphur trifluoride

C4H10 ----> tetracarbon decahydride

CO ----> carbon monoxide


How do you write a covalent compound formula?

1. Write the first element's symbol corresponding to its name.
2. Write the second elemen's symbol corresponding to its name.
3. Write in any prefixes if neccessary.

Examples:

carbon disulphide ----> CS2

xenon octafluoride ----> XeF8


Here's a table of commonly used prefixes for covalent compounds: