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ICSE Class 7 Chemistry Question 7 of 16

Atomic Structure — Question 12

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Question 12

Give the symbol and valency of the following elements and radicals.

(a) Potassium

(b) Sodium

(c) Hydrogen

(d) Calcium

(e) Aluminum

(f) Magnesium

(g) Zinc

(h) Chlorine [chloride]

(i) Sulphur [sulphide]

(j) Nitrogen [nitride]

(k) Oxygen [oxide]

(l) Ammonium

(m) Bicarbonate

(n) Nitrate

(o) Bisulphate

(p) Bisulphite

(q) Hydroxide

(r) Carbonate

(s) Sulphate

(t) Sulphite

Answer
S.
No.		Element/RadicalsSymbolValency
(a)PotassiumK++1
(b)SodiumNa++1
(c)HydrogenH++1 or -1
(d)CalciumCa2++2
(e)AluminiumAl3++3
(f)MagnesiumMg2++2
(g)ZincZn2++2
(h)Chlorine [chloride]Cl--1
(i)Sulphur [sulphide]S2--2
(j)Nitrogen [nitride]N3--3
(k)Oxygen [oxide]O2--2
(l)AmmoniumNH4++1
(m)BicarbonateHCO3--1
(n)NitrateNO3--1
(o)BisulphateHSO4--1
(p)BisulphiteHSO3--1
(q)HydroxideOH--1
(r)CarbonateCO32--2
(s)SulphateSO42--2
(t)SulphiteSO32--2

ICSE Class VII Chemistry Chapter 3 15 Marks

Atomic Structure — Quick Study Guide

Atoms are the building blocks of all matter. Understanding atomic structure is essential for all of chemistry.

Key Definitions

  • Atom: Smallest particle of an element with its chemical properties
  • Molecule: Group of two or more atoms bonded together
  • Element: Pure substance with only one type of atom
  • Compound: Two or more different elements chemically combined
  • Atomic number (Z): Number of protons = Number of electrons
  • Mass number (A): Protons + Neutrons
  • Valency: Combining capacity of an element
  • Isotopes: Same element, different mass numbers

Electronic Configuration Rules

K shell = max 2 electrons, L shell = max 8, M shell = max 8 (for first 20 elements). Fill inner shells first.

Exam Tips

  • Memorise symbols of first 20 elements
  • Practice calculating protons, neutrons, electrons from Z and A
  • Practice drawing Bohr diagrams
  • Valency: if outermost ≤ 4, valency = outermost; if > 4, valency = 8 - outermost

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