– Ionization energy of an atom is the amount of energy needed to remove an electron from itself.
– Electronegativity of an atom refers to its tendency to attract electrons.
– Electron affinity of an atom refers to the amount of energy given out when an electron is added to a neutral atom to form a anion.
– All three ionization energy, electronegativity and electron affinity of an atom decrease down a group but increase across a period. The higher the ionization energy, electronegativity and electron affinity, the more non-metallic characteristics an atom has. The opposite also holds true that with lower ionization energy, electronegativity and electron affinity, the more metallic characteristics an atom would have.
– Some differences between metals and non-metals are shown in the table below:
| Metals | Non-metals |
|---|---|
| Usually strong and hard,ductile and malleable | Usually weak and soft and cannot be bent, stretched or drawn into wires |
| Generally have high melting and boiling points (with the exception of Group I metals) | Generally have low melting and boiling points (with the exception of boron, carbon and silicon) |
| Usually solids at room temperature (with the exception of mercury) | Usually gases at room temperature (with the exception of boron, carbon, silicon, phosphorus, sulphur, bromine and iodine) |
| Good conductors of heat | Poor conductors of heat |
| Good conductors of electricity | Poor conductors of electricity (with the exception of carbon or graphite) |
| Always form cations | Usually form anions |
| Usually forms ionic bonds | Usually forms covalent bonds |
| Forms basic or amphoteric oxides | Forms neutral or acidic oxides |
– Amphoteric oxides of metals have some of both acidic and basic properties. (See: Acids, Bases and Salts)
Transition Metals
– Are a group of metals in the middle of the Periodic Table
– Have the following physical and chemical properties:
- Very high melting and boiling points
- Very high densities
- Variable number of valence electrons –> can have different oxidation states eg. $Cu^{+}$, $Cu^{2+}$, $Fe^{2+}$, $Fe^{3+}$
- Form coloured compounds
eg. $Cr^{2+}$, $Cu^{2+}$ and $V^{4+}$ form blue compounds,
$Cr^{3+}$, $Fe^{2+}$, $Mn^{6+}$, $Ni^{2+}$ and $V{3+}$ form green compounds,
$Co^{2+}$ and $Mn^{2+}$ form pink compounds,
$Co^{3+}$, $CrO_{4}^{2-}$ and $Fe^{3+}$ form yellow compounds
$Cr_{2}O_{7}^{2-}$ forms orange compounds and
$Mn^{7+}$ forms violet compounds - Not as reactive as metals in Group I and Group II
- Are good catalysts
– Uses of transition metals:
| Transition Metals | Uses |
|---|---|
| Iron | As a catalyst in the Haber Process to manufacture ammonia gas |
| Nickel | As a catalyst in the manufacturing of magarine |
| Vanadium | As a catalyst in the Contact Process to manufacture sulphuric acid |
| Titanium | In aircraft construction, making spectacle frames and watches due to its non-corrosive and strong yet light properties |
| Tungsten | Filament for light bulbs because it is ductile and has high melting points |
