Science Notes
Chemistry Notes: Predicting Types of Bonds
Now that you are familiar with three types of bonds: ionic bonds, covalent bonds, and metallic bonds, is there a way to predict which type of bond will form? Yes, by knowing some of the properties of the elements
Look at a periodic table.
Elements on the left side and in the center are metals, so they have metallic bonds.
Compounds formed between elements that lose
electrons easily and those that gain electrons easily form ionic bonds.
Elements on the left side and in the center of the periodic table tend to lose
electrons easily. These elements are metals.
Elements on the right side of the periodic table tend to gain electrons easily. These elements are nonmetals.
A compound formed between a metal and non-metal will thus have ionic bonds.
Compounds formed between elements that have similar tendencies to gain will have covalent bonds.
Bonds between nonmetals, on the right side of the periodic table, will have covalent bonds.
Combining Capacity of Atoms
The number of electrons an atom gains, loses, or shares when it forms chemical bonds is called its oxidation number. The oxidation number of an atom describes its combining capacity.
Sodium (Na) has 1 valence electron. It loses
one electron when it
combines to another atom. It forms an ion with a 1+ charge, Na 1+
Magnesium (Mg) has 2 valence electrons. It
loses two electrons when
it combines to another atom. It forms an ion with a 2+ charge, Mg 2+
Chlorine (Cl) has 7
valence electrons. It gains one electron when
it combines to another atom. It forms an ion with a 1- charge, Cl 1-
Using Oxidation Numbers
You can use the oxidation numbers of atoms to predict how atoms will combine and what the formula for the resulting compound will be.
You must know that the sum of the oxidation
numbers of atoms in a compound must be zero.
Example: Mg 2+ combines with two atoms of Cl 1- to
form MgCl2