Allied solutions simplified middle school chemistry class 7 Solutions for Chapter 4 atomic structure

Q1) State the meaning of the term – (a) atom (b) molecule (c) radical – with a suitable example.

Q2) Draw the basic structure of an atom representing its – (a) Subatomic particles (b) Nucleus (c) Orbits or shells.

Q3) In the modern periodic table – atoms of all elements are arranged according to their increasing order of – the atomic number. An atom of nitrogen has seven protons and seven electrons. State what would be its atomic number.

Q4) State the main points of the contradiction of Dalton’s atomic theory by the modern atomic theory.

Q5) ‘Atoms of the same element or different of Dalton’s atomic theory by the modern atomic theory’. Give two examples each of =-

1. Atoms of the same element
2. Atoms of different elements combining to form a molecule.

Q6) Explain the term – ‘atomicity’. Give a reason why –

1. Helium is considered monoatomic, but hydrogen is a diatomic molecule.
2. Ozone is considered triatomic, but phosphorus a tetratomic molecule.

Q7) State the atomicity of the following:

1. Neon
2. Oxygen
3. Chlorine
4. Argon
5. Sulphur

Q8) 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.

Q9) Differentiate between the following with suitable examples – A basic radical and an acid radical.

Q10) Name the cation and the anion in the salt – calcium sulphate.

Q11) Explain the term – ‘valency’. State giving reasons the valency of –

1. Chlorine in hydrogen chloride
2. Sulphate in sulphuric acid
3. Nitrogen in ammonia
4. Magnesium in magnesium oxide.

Q12) Give the symbols and valency of the following elements and radicals.

1. Potassium
2. Sodium
3. Hydrogen
4. Calcium
5. Aluminium
6. Magnesium
7. Zinc
8. Chlorine
9. Sulphur
10. Nitrogen
11. Oxygen
12. Ammonium
13. Bicarbonate
14. Nitrate
15. Bisulphate
16. Bisulphite
17. Hydroxide
18. Carbonate
19. Sulphate
20. Sulphite

13) Give an example of three elements exhibiting variable valency.

Q14. State what is meant by the term – ‘chemical formula’. Give the chemical formula of –

a) Sodium hydroxide

b) Sodium nitrate

c) Sodium bicarbonate

d) Sodium sulphite

e) Magnesium nitrate

f) Ammonium sulphate

g) Carbonic acid

h) Calcium phosphate

Q15) Dilute hydrochloric acid is added to sodium hydroxide’. Give a word equation and a molecular equation of the same. Is the equation written, a balanced equation. Give reasons.

Q16) State what the group number in the Modern Periodic Table signifies. Give a reason why elements in the same group, have similar valency and similar chemical properties.

Q1) Fill in the blanks with the correct words from the brackets.

1. A molecule of an element is _____
2. A radical with one atom of sulphur and three atoms of oxygen is ______
3. An element with variable valency is _______
4. The formula for aluminium sulphide is __________
5. the element lithium in the modern periodic table with valency 1^+ belongs to the group _____

Q2) Select the correct answer from A,B,C,D and E for each statement given below:

A: Molecule B: Orbits C: Atom D: Valency E: Radical

1. The basic unit of matter not capable of independent existence.
2. The smallest particle of a substance – capable of independent existence and which retains the characteristics of the substance
3. An elementary particle of matter – of a group of atoms of different elements behaving as a single unit with charge on the group.
4. Imaginary path around the nucleus of an atom in which electrons revolve.
5. The term for the combining capacity of an element or the number of hydrogen atoms with which it combines or replaces.

Q3) Match the radicals in List I with their correct names from List II

Q4) State the correct formula of the following from the list given:

1. Calcium hydroxide – Ca_2OH\ /Ca\left(OH\right)_2/CaOH
2. Sodium bisulphite – NaHSO_4/Na_2HSO_3/NaHSO_3
3. Ammonium sulphate – \left(NH_4\right)_2SO_4/NH_4SO_3/\left(NH_{\text{4}}\right)_2SO_3
4. Ammonium phosphate – Al_2\left(PO_4\right)_3/AlPO_4/Al_2\left(PO_4\right)_2
5. Copper nitrate – Cu\left(NO_3\right)_2/Cu_2NO_3/CuNO_3

Q5) Name the following

1. A molecule of a compound containing two oxygen atoms and one nitrogen atom.
2. The radical containing one nitrogen and four hydrogen atoms.
3. The compound formed when iron \left[Fe^{2+}\right] combines with oxygen \left[O^2\right]
4. The group of Modern Periodic Tqable to which calcium \left[Ca^{2+}\right] belongs.
5. A non metal which forms a polyatomic molecule with more than three atoms.