Metals and non-metals
Francine Taylor Campbell, Contributor

Herbert Morrison Technical High School students walk towards their next class minutes before the end of the school lunch period. - Claudine Housen Photo

POINTS TO NOTE

* Metals are generally found in groups 1, 2 and 3 of the periodic table.

* A metal describes an element that ionises by losing electrons and is referred to as being electropositive.

* Metals are reducing agents.

* Most metals react with dilute acids, water and steam. The oxides of metals are basic (except for Al, Zn and Pb) and react with acids to form salt and water.

* Metals exhibit the following physical properties; high melting and boiling points, good electrical and thermal conductivity, solids at room temperature (except for Hg) and easily bent or drawn into wires.

* The bonding in metals is responsible for their physical properties.

* Non-metals are generally found between groups 5 and 7 of the periodic table.

* A non-metal is an element which forms ions by gaining electrons and is said to be electronegative.

* Non-metals are oxidising agents as they react by gaining electrons.
N + n e ===== Nn-.

* Non-metals react with air or oxygen to form acidic oxides which can dissolve in water to form acids.

* Non-metals do not react with dilute acids, water or steam.

* They form covalent compounds with other non-metals and ionic compounds with metals.

As stated earlier, metals undergo reactions with acids, oxygen, water and steam. The ease with which these reactions occur is dependent on the position of the metal in the reactivity series. This is a list of metals arranged in order of their reactivity or how readily they will lose their outer electrons. A metal that will readily give up its electrons (e.g. K) is more reactive than one that loses electrons less readily (e.g. Cu). Metals at the top of the series are the most electropositive and the ones at the bottom are the least electropositive.

The reactivity series of metals

K	Most reactive
Na
Ca		Decreasing reactivity, ease of Mg ionisation, stability of
Al		compounds and strength as reducing agents.
Zn
Fe
Pb
(H)
Cu
Hg
Ag
Au	Least reactive

SUMMARY OF THE REACTIONS OF METALS

1. Metals react with air or oxygen to form oxides

2Ca + O2 == 2CaO calcium oxide

Ag and Au has no reaction with oxygen

2. Metals react with water or steam to form the oxide or hydroxide

Na, K and Ca react with cold water to form the hydroxide and hydrogen

2Na + 2H2O (l) == 2NaOH + H2

Metals above Pb react with steam to produce the oxide and hydrogen

Mg + H2O (g) == MgO + H2

Below this there is no reaction with water or steam

3. With dilute acids the metals higher up in the series react violently forming salt and hydrogen. As you go down the list the reaction is less vigorous until you reach Pb, Cu, Ag and Au, which has no reaction.

4. The thermal stability of the nitrates, carbonates and hydroxides of metals is also based on the reactivity series. The ease with which these compounds decompose when heated, increases as you go down the series. (See text for an outline of these reactions)

The reactivity of a non-metal is based upon how readily it gains electrons or its affinity for electrons. For example in Group 7 of the periodic table, the halogens, the most reactive element is at the top of the group. This is because its outer shell is closer to the nucleus than the element at the bottom of the group, hence its attracting power for electrons is greater. So fluorine is more reactive and electronegative than chlorine, which is more reactive than bromine.

* Francine Taylor-Campbell is an independent contributor.