This occurs in metals and is when electrons are given out from the metal atoms to
make a "sea" of free electrons in between all of the metal atoms. These free electrons
hold the metal as a mass together. This is known as being a giant structure.
The free electrons present make it possible for electricity to be transferred easily
because the charge is carried by them. Because the metal atoms have lost electrons,
they have a positive charge.
This occurs typically between a metal and a non-metal (from groups 1 + 2 and 6 + 7
on the periodic table). The metal atom loses electrons which are taken by the non-
metal. Therefore, the metal ion produced has a positive charge and the non-metal ion
is negatively charged.
Sodium (metal - group 1) + Chlorine (non-metal - group 7) ----> Sodium
In the example below, the sodium atom has lost an electron to form a positive ion.
The chlorine atom has gained the electron lost from the sodium to form a negative
ion. The NaCl molecules are arranged in a giant structure to form the substance more
commonly known as Salt.
This is when electrons are shared between atoms. Covalent bonding occurs between
non-metals due to the fact that all of the atoms need to gain electrons, so they have to
Common substances that covalent bonding occurs in: Water (H O), 2ydrogen gas
(H 2, and Methane (CH ) 4 FRACTIONAL DISTILATION
Fractional distillation is the process of heating up a mixture containing different
substances with different boiling points, and drawing the different fractions off as
they each boil and liquify at its own level. Crude oil contains a lot of useful
substances that can be used for different purposes.
Each fraction is not a pure compound but is a mixture of different alkanes with similar
boiling points. Fractional distillation is used because the substances in crude oil are
miscible (which means that they mix) therefore they do not separate out into layers.
The following table shows the products of fractional distillation:
Boiling Point Uses of Fraction