Video Transcript
A magnesium atom has the chemical
formula Mg. What is the chemical formula of the
magnesium ion?
A chemical formula is an expression
used to represent an atom, ion, or compound. We are told in the question that
the chemical formula of a magnesium atom is Mg. We need to determine the chemical
formula of the magnesium ion.
An ion is an atomic or molecular
particle with a net electric charge. The chemical formula of an ion
consists of the chemical formula of the corresponding atom or molecule with the
charge written as a superscript to the right of the chemical symbol. So, the chemical formula of the
magnesium ion will consist of the chemical symbol for magnesium, Mg, with the charge
of the ion written to the right as a superscript.
The location of an element on the
periodic table can sometimes help us to determine the most likely charge an ion of
that element would have. For example, group one metal ions
typically have a charge of one plus, while group two metal ions typically have a
charge of two plus. The halogens of group 17 typically
form ions with a charge of one minus. Many group 16 elements form ions
with a charge of two minus, and some of the group 15 elements are likely to form
ions with a charge of three minus.
The element magnesium is found in
group two of the periodic table, so a magnesium ion is likely to have a two plus
charge. We can write the charge two plus as
a superscript to the right of the symbol Mg to complete the chemical formula of the
magnesium ion. So the complete chemical formula of
the magnesium ion is Mg2+.
