Metals & Non metals
There are 115 elements known till today. These elements can be classified into various groups on the basis of their properties. Metals are usually hard, malleable and ductile. They are sonorous and have metallic lustre. They are good conductors of heat and electricity.
Non-metallic are usually soft. They do not possess lustre. They are not malleable and ductile rather they are brittle. They are not good conductors of heat and electricity.
We shall study about metals and non-metals in detail.
IMPORTANT TERMS AND CONCEPTS
Definition of Metals?
Those elements which can lose electrons easily and from positive ions. They are mostly solids, possess high density. They have high melting and boiling points. They have metallic lustre and they are sonorous, i.e., produce metallic sound. They are good conductors of heat and electricity. They are usually malleable and ductile, e.g., gold , silver, copper, tin, lead, iron, mercury, cobalt, nickel, aluminium, sodium, potassium are metals.
Most of the metals are hard. If you try to cut them with knife, it will not be possible in most of the metals. Some of metals like sodium, potassium are soft metals and can be cut with knife.
The ability of a metals due to which it can be beaten into sheets is called malleability. Iron, copper, zinc, aluminium, magnesium are available in the form of sheets. Aluminium, steel, copper, brass, bronze are used in making utensils.
Brass and bronze are also used for making statues. Bronze is used for making medals. Aluminium and silver metals are converted in foils. Aluminium foils are used for packaing whereas silver foils are used in decorating sweets.
It is the ability of metals due to which it can be drawn into wires. Copper, aluminium, iron can be drawn into wires. Silver, gold and platinum are highly ductile metals. 1 gram of gold can be drawn into 2 km long wire.
Effect of Tapping (Sonorous)
When metals are struck with hard substance, they produce sound, i.e., they are sonorous. Brass and bronze are highly sonorous. They are used in making bells and gongs.
It is the property due to which electric current can pass through the metal. It is due to presence of free electrons or mobile electrons, e.g., copper, silver, gold, aluminium are good conductors of electricity. Silver is best conductor of electricity followed by copper, gold, aluminium and tungsten. Mercury and lead have low electrical conductivity due to high resistance.
It is the property due to which metals can conduct heat e.g., copper, silver, aluminium, gold and iron are good conductors of heat.
Most of metals have shiny surface i.e., they show metallic lustre e.g., Au, Ag, Pt are lustrous.
Exceptions if classification of metals and non-metals is done on the basis of physical properties :
- All metals are hard except sodium, potassium, lithium, They can be cut even with knife. Osmium (Os) is hardest metal. Lithium is lightest metal.
- All metals are solids except mercury. Cesium, francium, germanium and gallium are low melting solids. Gallium becomes liquid if kept on palm. But gallium has very high boiling point which makes it useful for high temperature thermometers.
- Iodine is a non-metals but has metallic lustre. Diamond (an allotrope of carbon) is highly lustrous.
- Non-metals have low melting and boiling points but diamond, graphite, boron and silicon have high melting and boiling points.
- Metals have high melting and boiling points. Tungsten has highest melting point whereas sodium, potassium have low melting and boiling points.
- Non-metals are bad conductors of heat and electricity, but graphite is a non-metals which is good conductor of heat and electricity.
- Metals generally have high density e.g., Cu, Cr, Ag, Au, Pt, Os, Ir, Ti, W, etc. Sodium, potassium, and lithium have density less than 1 g cm–3. Diamond is non-metals but still has high density.
- Generally, metals have 1 to 3 valence electrons. Hydrogen has one valence electron but still it is non-metal. Helium has 2 valence electrons but still it is non-metals.
- Metals usually have a bright metallic lustre and are silvery white in appearance, but gold is yellow in colour, copper is reddish brown.
- Non-metals generally do not from alloys but carbon is alloyed with iron to form steel.
Thus metals and non-metals cannot be classified on the basis of physical properties only. Chemical properties are more suitable to classify them.
The process of forming oxide layer on the surface of metal is called anodising, e.g., Aluminium forms an oxide layer on its surface when exposed to air. It is non-penetrating layer which protects it from corrosion. The layer can be made more thick with the help of anodising. It is a process in which cleaned aluminum metals is taken as anode. Dilute H2SO4 acts as electrolyte. When electric current is passed, O2 gas is liberated which reacts with aluminium to form a layer of aluminium oxide.
The oxide layer can be made coloured like red, blue, etc., so as to make it more attractive for making decorative articles.
Metal burns in presence of oxygen to from metal oxide. Let us perform and experiment.
Solubility of Oxides in water
Some metal oxides are soluble in water. Soluble base are called alkalies e.g.,
Those base, which are soluble in water are called alkalies. For example, sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide Ca(OH)2 They turn phenolphthanlein pink and turn red litmus blue.
Those oxide, which react with acids or acidic or acidic oxides to form salt and water are called basic oxides. Metals react with oxygen to form metallic oxides which are generally basic in nature e.g., Na2O (sodium oxide.) CaO (calcium oxide), K2O (potassium oxide), MgO (magnesium oxide) are basic oxides.
MgO + HCl → MgCl2 + H2O
Those oxides, which react with bases or basic oxides to form salt and water, are called acidic oxides. Non-metals react with oxygen to form non-metallic oxides which are generally acidic in nature, e.g., CO2 (carbon dioxide), SO2 (sulphur dioxide), SO3 (sulphur trioxide), P2O5 (phosphorus pentoxide), SiO2 (silicon dioxide) are acidic oxides.
CO2 + 2NaOH → Na2CO3 + H2O
These oxides are both acidic as well as basic in nature. They react both with acids as well as bases to form salt and water. Some metals form amphoteric oxides. ZnO (zinc oxide) and Al2O3 (aluminium oxide) are amphoteric oxides.
ZnO + 2HCl → ZnCl2 + H2O
These oxides are neither acidic nor basic in nature. They neither react with acids nor with bases. Some non-metals form neutral oxides. Carbon monoxide (CO), nitrogen oxide (NO), Nitrous oxide (N2O) are examples of neutral oxides.
The compounds in which metal loses electrons and non-metal gains electrons are called electrovalent compounds, e.g., NaCl (sodium chloride), KCl (potassium chloride), etc.
When metals react with hydrogen, the compounds formed are called hydrides. e.g., sodium hydride (NaH), calcium hydride (CaH2). In these compounds, metals lose electrons whereas hydrogen gains electron.
Reaction of metal oxides with Acids
Metal oxides react with acid to form salt and water because most of the metal oxides are basic or amphoteric in nature. Amphoteric oxides react with both acids as well as bases.
Na2O + 2HCl(dil) → 2NaCl + H2O
CaO(s) + H2SO4(dil) → CaSO4 + H2O
MgO(s) + 2HCl(dil) → MgCl2 + H2O
CuO(s) + 2HCl(dil) → CuCl2 + H2O
CuO(s) + H2SO4(dil) → CuSO4 + H2O
Fe2O3(s) + 6HCl(dil) → 2FeCl3 + 3H2O
SnO2 + 4HCl → SnCl4 + 2H2O
PbO + 2HCl → PbCl2 + H2O
PbO + H2SO4 → PbSO4 + H2O
AlP3 + 6HCl → 2AlCl3 + 3H2O
HgO + 2HCl → HgCl2 + H2O
HgO + H2SO4 → HgSO4 + H2O
ZnO + 2HCl → ZnCl2 + H2O
ZnO + H2SO4 → ZnSO4 + H2O
ZnO + 2KOH → + H2O
Reactivity of Metals
All the metals do not react with the same rate. Some react very fast, some react moderately whereas others react very slowly e.g., sodium, potassium react with oxygen at room temperature vigorously to form oxide. They can catch fire in presence of moist air. These metals are kept in kerosene oil or benzene so as to protect them from formation of oxide and hydroxide in open air.
At room temperature, metals like Al, Zn, Cu, Mg, Sn, Pb form oxide layer on their surface and become dull. This oxide layer makes aluminium passive and does not allow it to react further with H2O, O2 and even conc. HNO3. Copper is less reactive and forms black coloured oxide and gives green coloured flame with blue tip in burner. Magnesium burns with dazzling light forming MgO. Silver, gold and platinum do not react with oxygen. Mercury forms red coloured oxide, HgO.
Reactivity Series of Metals
The series of metals in decreasing order of reactivity is called reactivity or activity series of metals. The metals at the top are most reactive whereas metals at the bottom are less reactive. The following is activity series of metals. The metals above hydrogen are more reactive than hydrogen. They can displace hydrogen from dilute acids and water. Metals below hydrogen are less reactive than hydrogen and cannot displace hydrogen from dilute acids and water.
Reaction of Metals with Water
Some metals like Na, K, Ca react with cold water vigorously to form hydroxide and liberate hydrogen gas. Some metals like Mg, Zn, Al react with hot water to form oxides and hydroxides and hydrogen gas. Some metals like Fe reacts with steam to form Fe3O4 and H2(g). Some metals like Cu, Ag, Au, Hg, Pb and Pt do not react with water at all because they are less reactive than hydrogen. Let us perform the following experiment.
Reaction of Metals with Acids
Metals react with dilute acids to from salt and hydrogen gas. The metal replaces hydrogen of the acid to from salt. Let us perform experiment to show the reaction of metals with acids.
It is mixture of conc. HCl and conc. HNO3 (nitric acid) in the ratio of 3 : 1. It can dissolve gold and platinum. Gold and platinum do not react with conc. HCl. They do not react even with conc. HNO3. They dissolve in aqua regia. Aqua regia is a strong oxidising agent due to formation of NOCl (Nitrosyl chloride) and chlorine produced by reaction of two acids. Aqua regia (Latin word for royal water) is a highly corrosive and fuming liquid. Therefore, it should be kept away from eyes and skin.
Reaction of metals with solution of other metal salts :
More reactive metal can displace less reactive metal from their salt solution. These reactions are called displacement reactions. Let is carry out these reaction experimentally.
Reason for difference in Reactivity of Metals
We have observed with the help of experiments that some metals are less reactive whereas other metals are more reactive. Let us find out the reason why are some metals more reactive whereas other metals are less reactive.
Metals are those elements which can lose electrons easily. The reactivity of metals will depend upon how easily metal can lose electron and form positively charged ion. Metals have 1 to 3 electrons whereas non-metals have 4 to 8 electrons. hydrogen and Helium have one and two electrons respectively but still they are non-metals because they cannot lose electrons easily. Boron has three valence electrons but still it is non-metals.
Electronic Configuration of elements and classification as Metals and Non-metals :
|S.No.||Element||Symbol||Atomic number||Electronic configuration
K L M N O
|3.||Neon||Ne||10||2, 8||8||Non-metal(noble gas)|
|9.||Sodium||Na||11||2, 8, 1||1||Metal|
|10.||Magnesium||Mg||12||2, 8, 2||2||Metal|
|11.||Aluminium||Al||13||2, 8, 3||3||Metal|
|12.||Potassium||K||19||2, 8, 8, 1||1||Metal|
|13.||Calcium||Ca||20||2, 8, 8, 2||2||Metal|
Reason for Metals for Losing Electrons
In the electronic configuration of elements, you have observed that noble gases have 8 electrons in their outermost shell and they are quite stable except helium which has two valence electrons. It is also quite stable.
It means all metals will try to lose electrons to acquire nearest noble gas configuration, e.g.,
Reason for Non-metals for Gaining Electrons
Non-metals can gain electrons to form negative ions so as to acquire stable noble gas configuration, i.e., 8 electrons in its outermost orbit.
Non-metals gain electrons to complete their octet.
A stable group of eight electrons in the outermost orbit of the atom.
The bond which is formed by loss and gain of electrons is called ionic or electrovalent bond.
2Cl + 2e– → 2Cl–
(Mg2+) is electron dot diagram.
→ Al3+ + 3e–
3F + 3e– → 3F–
(Al3+) is electron dot diagram.
→ 2Na+ + 2e–
O + 2e– → O2–
(Na+)2is electron dot diagram.
Properties of Ionic Compounds
- Ionic compounds are solids, e.g., NaCl, KCl, CuSO4, K2SO4, NaNO3 are solids.
- Ionic compounds are somewhat hard and brittle. It is due to strong force of attraction between them.
- Ionic compounds have closed packed structures, e.g., NaCl has face centred cubic structure.
- Ionic compounds have high melting and boiling points. It is because of strong force of attraction between oppositely charged ions, therefore, high energy is required to break the metallic bonds between ions.
- Ionic or electro valent compounds are soluble in water because they form ions in aqueous solution.
- Ionic compounds are insoluble in organic solvents like alcohol, acetone, ether, chloroform, carbon disulphide etc. because they do not form ions in organic solvents.
- Ionic compounds conduct electricity in molten state and in aqueous solution because ions carry current. The movement of ions take place towards oppositely charged electrode in electric field.
- They do not conduct electricity in solid state because ions are not free to move.
Conclusion : It shows that ionic compounds conduct electricity in aqueous solution. Corrosion. It is a process in which metal reacts with substance present in atmosphere to form surface compounds, e.g., silver metal turns black due to formation of Ag2S. Copper forms a greenish layer of CuCO3.Cu(OH)2 on its surface. Iron forms reddish brown coating of hydrated ferric oxide, Fe2O3×xH2O.
Distinctions between metals and Nonmetals
Distinctions based on physical properties
|1. Metals have lustre called metallic lustre.||Non-metals do not possess any metallic luster.
Exceptions : Iodine and graphite possess metallic lustre
|2. Metals are generally electropositive||Nonmetals are generally electronegative .
Exception : Hydrogen is a non-metal but it is electropositive.
|3. Metals are generally good conductors of heat and electricity.||Non-metals are generally bad conductor of heat and electricity.
Exception : Graphite is a non-metals but it is a good conductor of electricity. Hydrogen, though a nonmetal, is a good conductor of heat.
|4. Metals are usually solids at ordinary temperature.
Exception : Mercury is a metal but it is a liquid at ordinary temperature.
|Nonmetals are gases or solids at ordinary temperature.
Exception : Bromine is a non-metal but it is a liquid at ordinary temperature.
|5. Metals are malleable and ductile, have high density, and reflect light.
Exception : Sodium and potassium are metals but their densities are less than that of water
|Non-metals are not malleable and ductile, have low density, and do not reflect light.
Exception : Plastic sulphur is ductile.
|6. Metals when hammered emit a characteristic sound called metallic sound||Non metals do not emit metallic sound.|
Distinctions based on physical properties
|1. Metals form positive ions. Example: Na+, K+, Ca2+, Mg2+, Fe2+, etc.||Nonmetals form negative ions. Example: Cl–, S2–, N3–, etc.|
|2. Oxides of metals are basic in nature, i.e., the oxides of metals react with water to give bases or alkalis.
Na2O + H2O → 2NaOH
CaO + H2O → Ca(OH)2
|Oxides of nonmetals are acidic in nature, i.e., the oxides of nonmetals react with water to give acids.
CO2 + H2O →
SO2 + H2O →
SO3 + H2O →
|3. Metals dissolve in dilute acids to produce hydrogen gas.
Zn + H2SO4 → ZnSO4 + H2
Exceptions Some metals do not produce hydrogen when treated with an acid under ordinary circumstances.
|Nonmetals generally do not dissolve in dilute acids.|
|4. Metals in general do not combine with hydrogen.
Exception : Some metals (Na, Ca, Li, Be, etc.) combine with hydrogen to form non-volatile unstable hydrides.
|Nonmetals combine with hydrogen to form stable compounds.|
|5. Metallic chlorides are generally not hydrolyzed by water, or are only partially hydrolyzed.
NaCl + H2O → No hydrolysis
AlCl3 + 3H2O → Al(OH)3 + 3HCl
|Chlorides of nonmetals are usually hydrolyzed by water.
PCl3 + 3H2O → 3HCl + H3PO3
SiCl4 + 4H2O → Si(OH)4 + 4HCl
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