Remember: The total charge of an ionic compound is always zero.
With sodium chloride:
- the Chloride ion formed carries a 1- charge.
- The sodium ion carries a 1+ charge .
- The ions thus combine together in a ratio of 1 : 1
- and the formula is therefore NaCl:
Students will be assessed on their ability to:
1.28 describe the formation of ions by the gain or loss of electrons
1.29 understand oxidation as the loss of electrons and reduction as the gain of electrons
1.30 recall the charges of common ions in this specification
1.31 deduce the charge of an ion from the electronic configuration of the atom from which the ion is formed
1.32 explain, using dot and cross diagrams, the formation of ionic compounds by electron transfer, limited to combinations of elements from Groups 1, 2, 3 and 5, 6, 7
1.33 understand ionic bonding as a strong electrostatic attraction between oppositely charged ions
1.34 understand that ionic compounds have high melting and boiling points because of strong electrostatic forces between oppositely charged ions
1.35 understand the relationship between ionic charge and the melting point and boiling point of an ionic compound
1.36 describe an ionic crystal as a giant three-dimensional lattice structure held together by the attraction between oppositely charged ions
1.37 draw a diagram to represent the positions of the ions in a crystal of sodium chloride
Electrons are transferred..
A neat trick..
A simple way to work out the formula of an ionic compound.
You can use this to balance the charges and work out the formula of any combination of positive and negative ions.