1.6.1c draw electron configuration diagrams of cations and anions using dots or crosses to represent electrons AND 1.6.2b draw electron configuration diagrams for simple covalently bonded molecules, including those with multiple bonds and dative covalent bonds, using dots or crosses to represent electrons

BONDING

You should be able to:
- draw dot and cross diagrams for cations and anions with electronic configurations
- describe how ions are formed by transfer of electrons
- construct ionic half equations for electrolysis
- explain why metals form positive ions and non-metals form negative ions
- predict charges of ions in the periodic table

Dative covalent bond: when both electrons in a covalent bond are from the same atom.

If you look at the periodic table, you can see that the group number (along the top) is the same as the number of outer shell electrons.

Group 1 metals all become 1+ ions, group 2 make ions with a 2+ charge, group 3 make ions with 3+ ions, group 7 make ions with a 2- charge, group 7 make ions with a 1- charge.

Transition metals have more complicated shells so they have several different + charges, depending on how oxidised they have become (eg. Fe2+ or Fe3+)

Group 0 or 8 are the noble gases, they are stable and inert and have full outer shells.

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PRACTICE QUESTIONS

1. Draw a diagram (using dots or crosses) for the ions in magnesium fluoride showing all the electrons and the ionic charges on:

i) the magnesium ion

ii) the fluoride ion

2. Chlorine forms compounds with magnesium and with carbon.

i) draw a dot and cross diagram to show the electronic structure of the compound magnesium chloride (only the outer electrons need to be shown). Include the charges present.

ii) draw a dot and cross diagram to show the electronic structure of the compound tetrachloromethane (only the outer electrons need to be shown).

3.i) Define the term 'covalent bond'.

A covalent bond is formed when electron pairs are shared between non-metal atoms. The bonded atoms form a molecule. Covalent bonds have no free electrons or ions, so they cannot conduct electricity, and they are mainly gases or liquids at room temperature, as they have low melting and boiling points.

ii) Nitrogen forms an oxide called nitrous oxide (N2O). The bonding in nitrous oxide can be represented as: N---N-O

(--- is a triple bond)
Complete the diagram below for the N2O molecule using dots or crosses to represent electrons. Only show all of the outer electrons.

1.