Elements in the same group have similar properties due to their electronic configuration. However, the properties of these elements show variation down the group as electron shells increases. The changes that elements within a group undergo is known as group trend .

• They are univalent elements i.e they possess one valence electrons in their outermost shell.
• They ionize readily to form cations by donating their valence electron.
• They combine with non metallic ions to form electrovalent compounds.
• They are good reducing agents. Their reducing ability increases down the group.
• They are good conductors of electricity and are very electropositive.
• They react vigorously with cold water to form alkalis and liberate hydrogen gas. Hence they are called alkali metals . The reactivity with cold water increases down the group.
  2K_(s) + 2H₂O_(l) ————> 2KOH_(aq) + H_2(g)
  Their oxides also dissolve in water to form strong alkalis.
  Na₂O_(s) + H₂O_(l)————> 2NaOH_(aq)
  
  
• On heating, their trioxonitrate(V) salts decompose difficulty to liberate oxygen and dioxonutrate(III) salts.
  2NaNO₃ + heat —————> 2NaNO₂ + O_2(g)
  
  
• The solubilities of the carbonates of group 1 elements increases down the group. All carbonates of alkali metals are thermally stable except for lithium carbonate. The trioxocarbonates and tetraoxosulphates of alkali metals are soluble in water . The hydrogen trioxocarbonate(IV) of sodium decomposes readily on heating to yield its metallic carbonate and liberate carbon (IV) oxide.
  NaHCO₃ + heat ————> Na₂CO₃ + H₂O + CO_2(g)
  
  
• Members include Sodium, Lithium, Potassium, Francium, Caesium, Rubidium, Hydrogen which is placed there for convenience.

• They are divalent elements i.e they possess two valence electrons.
• They ionize by loosing their valence electrons to from +2 cations
• They are very reactive but less reactive than group 1 elements
• They form electrovalent compounds and are good reducing agents
• They react sparingly with cold water to liberate hydrogen gas. Magnesium reacts with steam to yield metallic oxide, Beryllium does not react with cold water or steam( but can at very high temperatures) while Calcium, Barium and Strontium reacts slowly with cold water to yield a metallic hydroxide and hydrogen gas. Be_(s) + H₂O_(g) —————> BeO_(s) + H_2(g) Mg_(s) + H₂O_(g) —————> MgO_(s) + H_2(g) Ca_(s) + 2H₂O_(l) —————> Ca(OH)_2(aq) + H_2(g)
• The solubilities of their oxides and hydroxides in water generally increases down the group. Magnesium oxide dissolves sparingly in water to form Magnesium hydroxide while Calcium oxide dissolves in water to form calcium hydroxide which is a weak alkali. They are generally called alkali earth metals .
  MgO_(s) + H₂O_(l) —————> Mg(OH)_2(aq)
  CaO_(s) + H₂O_(l) —————> Ca(OH)_2(aq)
  
  
• Their trioxonitrates(V) salts decompose readily on heating to liberate oxygen gas and brownish nitrogen (IV) oxide. Ca(NO₃)₂ + heat ————> 2CaO + O_2(g) + 4NO_2(g)


• Their trioxocarbonates (IV) salts are insoluble in water and they decompose heating to yield carbon(IV) oxide.
  CaCO₃ + heat ————> CaO + CO_2(g) MgCO₃ + heat ————> MgO + CO_2(g)
  
  
• Their members include Beryllium, Magnesium, Calcium, Strontium, Barium, Radium.

• They are trivalent elements i e they possess three valence electrons.
• They are reducing agents and ionize by the lose of three valence electrons
.
• They form elecrovalent compounds with nonmetals.
• Aluminum reacts with steam at 750°C to liberate hydrogen gas.
  2Al + 3H₂O —————> Al₂O₃ + H₂
• Aluminum oxide is insoluble in water.
  Both the oxides and hydroxides of Aluminum are amphoteric in nature i.e they have both acidic and basic properties. They can form normal and complex salts with acids and alkalis respectively.
  Al₂O₃ + 3H₂SO₄ —————> Al₂(SO₄)₃ + 3H₂O

       (acid)  (normal salt) 

  Al₂O₃ + 2NaOH + 3H₂O —————> 2NaAl(OH)₄

        (alkali)      (complex salt) 
        

• The trioxonitrate (V) of aluminum decomposes on heating to yield brown nitrogen (IV) oxide. 4Al(NO₃)₃ ————> 2Al₂O₃ + 3O₂ + 12NO₂
  
• The members include Boron, Aluminum, Galium, Indium,Thalium

• They are tetravalent elements
• They form covalent compounds with elements like oxygen, hydrogen. Carbon combines with hydrogen to yield hydrocarbons.
• The compounds of group (IV) elements exhibit +2 and +4 oxidation states. The stability of +2 increases and that of +4 decreases down the group.
• They show a group trend changing from non-metals to metals on going down the group. Carbon is a nonmetal, silicon and germanium are metalloids while tin and lead are metals.
• The electronegativity of group 4 elements decreases down the group from non-metals to metals.
• Carbon does not react with copper in any form but silicon and tin react with steam to form +4 oxides and hydrogen.
  Si + 2H₂O ————> SiO₂ + 2H_2(g)
• Lead forms lead(II) hydroxide with aerated water. Carbon, silicon and tin forms +4 oxides when heated strongly with air or oxygen. Lead forms lead(II) oxide on heating on air.

• They are good oxidizing agents
• They accept two electrons fo form 2- anions
• They combine electrovalently with metallic ions or covalently with nonmetals
• They possess six valence electrons in their outermost shell
• Oxygen and sulphur reacts with hydrogen to yield water and hydrogen sulphide respectively
• Oxygen is soluble in water while sulphur is not
• Group 6 elements include Oxygen, Sulphur, Selenium, Tellurium, Polonium

• They are called halogens or salt formers
• They are the most reactive non metals
• They exist as diatomic molecules
• They are strong oxidizing agents
• They are colored. Flourine is yellow, Chlorine is greenish-yellow, Bromine is reddish brown, Iodine is violet-black(grey-black), and Astatine is black.
• They have seven valence electrons in their outermost shell
• They ionize by gain of one electron to form negatively charged ions to form electrovant compounds with metallic ions.
• Their hydrides are covalent gases at room temperature and dissolve readily in water to yield acids
• They show group trend going down the group due to increase in subshells.
  • Flourine and chlorine are gases, bromine is a liquid, iodine and astatine are solids at room temperature
  • Melting and boiling points increases progressively
  • Chemical reactivity decreases down the group. Hence flourine is the most reactive while Astatine is the least.
    At < I < Br < Cl < F
  • Flourine reacts explosively with hydrogen even in dark, Chlorine in diffuse light but explosively in bright light, bromine slowly in bright light and iodine slowly and incompletely even in bright light to give their corresponding halides.
    F₂ + H₂ —————> 2HF_(g)
    Cl₂ + H₂ —————> 2HCl_(g)
    Br₂ + H₂ —————> 2HBr_(g)
    I₂ + H₂ <—————> 2HI_(g)
  • Elements higher up in the group displaces elements lower down in the group

• They are known as noble or rare gases
• They are inert in nature. They are relatively unreactive due to the completion of their outermost shell. Hence they are stable.
• They exist as free monoatomic molecules in the atmosphere
• They constitute about 1% of the composition in air
• They possess 8 electrons(2 in the case of Helium) in their outermost shell.
• They bear no resemblance to halogens and alkali metals
• Members include Helium, Neon, Argon, Krypton, Xenon, and Radon
• They exhibit group trends moving down the group due to increase in atomic number
  • Melting and boiling points increases down the group
  • Ionization energy decreases down the group