4.1.1 Describe the ionic bond as the electrostatic attraction
between oppositely charged ions.
An ionic bond is a the electrostatic attraction between oppositely charged ions.
The greater the charge difference, the greater the force of attraction between the ions. (E.g. Magnesium Chloride has a stronger ionic bond than Sodium Chloride because there is a greater ionic charge difference between MgCl2 than NaCl)
4.1.2 Describe how ions can be formed as a result of
electron transfer
Ions are formed by the transfer of electrons:
Cations are formed by the removing of electrons from an atom.
Anions are formed by the gaining of electrons from another atom.
4.1.3 Deduce which ions will be formed when elements in
Groups 1, 2, 3 lose electrons
Group 1 loses 1 electron, therefore ions with a 1+ charged are formed, because there is now one "extra" proton in the nucleus, so the atom now has a positive charge, this is what we call a 'cation'.
Group 2 has an ionic charge of 2+
Group 3 has an ionic charge of 3+
4.1.4 Deduce which ions will be formed when elements in
Groups 5, 6, 7 gain electrons
Group 5 gains electrons, as it 'wants' to complete it's outer shell (8 electrons). It has 5 electrons on it's outer shell already, so it gains 3 more, meaning there are 3 'extra' electrons, thus giving it a 3- charge. Negatively charged ions are called 'anions'
Group 6 has an ionic charge of 2-
Group 7 has an ionic charge of 1-
(Group 8 elements all have full outer shells, so it is very difficult for them to form ions.)
4.1.5 State that transition elements can form more than one
ion
Transition metals are based between Group 2 and Group 3 on the Periodic Table.
Transition metals like copper and iron can have more than one ion; its ions are also coloured.
Copper (Cu), for example, can form 2+ and 1+ ions, it's Cu 2+ ion is blue, while Cu 1+ is pale yellow; and iron (Fe) can form 2+ and 3+ ions, Fe 2+ gives a pale green colour, Fe 3+ gives a orangey-brown colour.
4.1.6 Predict whether a compound of two elements would be
ionic from the position of the elements in the Periodic Table or from their
electronegativity values.
Ionic bonds are only formed between metal + non-metal ions.
To predict the type of bond from it's position in the Periodic Table. Firstly you have to know where the different types of elements are.
To predict the type of bond from their electronegativity values you have to find the difference between their electronegativities. If the difference is GREATER than 1.75, this means that the bond has a more ionic character, (lower than 1.75 means the bond has a more covalent character)
4.1.7 State the formula of common polyatomic ions formed by
non-metals in period 2 and 3
Polyatomic ions are ions formed with more than 1 ion. E.g. HCO3-, OH-, NO3-
4.1.8 Describe the lattice structure of ionic compounds
Ionic compounds are often described as having 'giant lattice structures' or 3D crystalline structures.
The higher the charges on the ions, the smaller the size; and the larger the lattice enthalpy, the more energetically stable the ionic compound.
