Definitions [4]
Metals are reactive. They lose electrons easily and become positively charged ions. That is why metals are called electropositive elements.
Non-metals, except hydrogen, are the elements which form negative ions by the gain of electrons.
Certain elements which show properties of both metals and non metals are called metalloids or semi-metals.
Nonmetals are called electronegative elements because they form negatively charged ions by accepting electrons.
Chemica Equations [4]
\[\mathrm{C}\mathrm{l}_2(\mathrm{g})+\mathrm{H}_2\mathrm{O}(\mathrm{l})\longrightarrow\mathrm{H}\mathrm{O}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})+\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})\]
Nonmetals usually don’t react with water, except halogens like chlorine.
\[\mathrm{Cl}_{2}(\mathrm{g})+2\mathrm{HBr}\left(\mathrm{aq}\right)\longrightarrow2\mathrm{HCl}(\mathrm{aq})+\mathrm{Br}_{2}(\mathrm{aq})\]
Nonmetals usually don’t react with dilute acids, but halogens like chlorine do.
\[\mathrm{S}+\mathrm{H}_2\longrightarrow\mathrm{H}_2\mathrm{S}\]
\[\mathrm{N}_2+3\mathrm{H}_2\longrightarrow2\mathrm{NH}_3\]
Nonmetals react with hydrogen in special conditions.
\[\mathrm{C}+\mathrm{O}_2\xrightarrow{\text{Complete combustion}}\mathrm{CO}_2\mathrm{(Acidic)}\]
\[2\mathrm{C}+\mathrm{O}_2\xrightarrow{\text{Partial Combustion}}2\mathrm{CO~(Neutral)}\]
\[\mathrm{S}+\mathrm{O}_2\xrightarrow{\text{Combustion}}\mathrm{SO}_2\mathrm{(Acidic)}\]
Nonmetals form acidic or neutral oxides with oxygen.
Key Points
- Metals are mostly solids at room temperature; mercury and gallium are exceptions and exist in liquid form.
- Metals have a shining surface called metallic lustre, which may decrease due to oxidation or reaction with gases.
- Malleability allows metals to be beaten into thin sheets (gold and silver are highly malleable), and ductility allows them to be drawn into wires (gold is the most ductile).
- Metals are good conductors of heat and electricity, with silver and copper being excellent conductors.
- Most metals are hard with high melting and boiling points, but alkali metals (sodium, potassium) are soft and low‑melting, and metals are sonorous, producing sound when struck.
- Most metals form basic oxides with oxygen; aluminium and zinc oxides are amphoteric.
- Reactivity with oxygen varies; sodium and potassium react quickly and are kept in kerosene.
- Metals may react with water to form hydroxides and release hydrogen gas, depending on temperature.
- Metals react with dilute acids to give salt and hydrogen gas; copper and nitric acid are exceptions.
- More reactive metals can displace less reactive ones; this forms the basis of the reactivity series.
- Most metals are solids at room temperature, but mercury is a liquid, and gallium and caesium melt in the palm of the hand due to their very low melting points.
- Alkali metals (lithium, sodium, potassium) are soft, low-density metals with low melting points, unlike most metals.
- Iodine, though a non-metal, shows a metallic lustre, which is unusual for a non-metal.
- Carbon exists in allotropes: diamond is the hardest natural substance, and graphite is a good conductor of electricity.
- Nonmetals are usually non-lustrous, soft, poor conductors, and exist in solid or gas states, with bromine being the only liquid non-metal.
