Definitions [11]
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.
Corrosion is the gradual damage of metals caused by their reaction with components of the atmosphere, such as oxygen and moisture.
Define:
Alloy
A homogeneous mixture of two or more metals or metals with non-metals is known as an alloy.
For example - Duralumin is a homogeneous mixture of aluminium, copper, magnesium and manganese.
A steel containing up to 10% of elements such as chromium, molybdenum, nickel, etc., usually with a low percentage of carbon is known as alloy steel.
An alloy is a homogeneous mixture of two or more metals or of one or more metals with certain non-metallic elements.
Alloys melting in the range of about 51 °C to 260°C, usually contain bismuth, lead, tin, etc. These alloys are called fusible alloys.
Dental amalgam is a mixture of mercury and a silver-tin alloy.
A mixture or an alloy of mercury with a number of metals or alloys such as sodium, zinc, gold and silver as well as with some non metals is known as amalgam.
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.
