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ICSE Class 7 Chemistry Question 4 of 16

Atomic Structure — Question 8

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Question 8

'A radical takes part — unsplit in a chemical reaction and retains its identity in reactions'. With reference to the radical:

(a) ammonium

(b) bisulphate

(c) carbonate — state the group of atoms present in each radical.

Answer

(a) Ammonium [NH4]: 1 nitrogen atom and 4 hydrogen atoms

(b) Bisulphate [HSO4]: 1 hydrogen atom, 1 sulphur atom and four oxygen atoms

(c) Carbonate [CO3] : 1 carbon atom and 3 oxygen atoms

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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