Ex 4E Solutions| Atomic Structure and Chemical Bonding | Selina | Chemistry | Class 9 | ICSE

 ICSE
Class 9
Selina Solutions
Atomic Structure and Chemical Bonding
Ex 4E

Q1.

(a)         Define covalent (molecular) bond.

(b)         Give an example of covalent bond formed by:

(i) Similar atoms

(ii) Dissimilar atoms

Q2. Covalent bonds can be single, double or triple covalent bond. How many electrons are shared in each? Give an example of each type.

Q3. Show number of bonds in:

(i) Ethene molecule

(ii) Ethyne molecule

Q4. An element A has 1 electron in its first shell. It combines with element B having 7 electrons in its third shell. What type of bond is formed?

Q5. Match the atomic numbers 4, 8, 10, 15 and 19 with each of the following:

(a) Element which can form trivalent ion

(b) An element with 4 shells.

(c) Element with 6 valence electrons.

(d) Element which does not form ion.

Q6. If electrons are getting added to an element Y; then 

(a) Is Y getting oxidised or reduced?

(b) what charge will Y migrate to during the process of electrolysis?

Q7. 

(a) Elements X, Y and Z have atomic numbers 6, 9 and 12 respectively. Which one:

(i) forms an anion

(ii) forms a cation

(b) State the type of bond between Y and Z and give its molecular formula.

Q8. Taking MgCl₂ as an example of electrovalent bond, CCl₄ as a covalent bond, give a difference between electrovalent and covalent bonds.

Q9. Potassium chloride is an electrovalent compound, while hydrogen chloride is a covalent compound. But, both conduct electricity in their aqueous solutions. Explain.

Q10. Name two compounds that are covalent when taken pure but produce ions when dissolved in water.

Q11. An element M burns in oxygen to form an ionic compound MO. Write the formula of the compounds formed if this element is made to combine with chlorine and sulphur separately.

Q12. Give orbital diagram of the following:

(a) Magnesium chloride

(b) Nitrogen 

(c) Methane

(d) Hydrogen chloride

Q13. State the type of bonding in the following molecules.

(a) Water

(b) Calcium oxide

(c) Hydrogen chloride

Q14. Metal M forms a chloride with the formula MCl₂. What type of bond is in MCl₂. Write the formula of the compound when M combines with sulphur, oxygen and nitrogen

Q15. Explain the following:

(a) Mass of an atom is concentrated inside the nucleus of the atom.

(b) Atoms combine by transfer and sharing of electron(s).

(c) An element has atoms with different mass number.

(d) Carbon-12 and carbon-14 both show similar chemical properties.

Q16. Choose the correct answer from the choices A, B C and D:

(i) The characteristic of an electrovalent compound is that:

A. They are formed by sharing of electrons.

B. They are formed between metals and non-metals.

C. They are formed between two non-metals.

D. They often exist as a liquid.

(ii) When a metal atom becomes an ion:

A. It loses electrons and is oxidized

B. It gains electrons and is reduced.

C. It gains electrons and is oxidized.

D. It loses electrons and is reduced.

Q17. Identify the following reactions as either oxidation or reduction.

(i)                     O + 2e^- ---→ O^2-

(ii)                   K – e^-  ----→ K⁺

(iii)                Fe³⁺ + e^- ---→ Fe²⁺

(iv)                 Zn --→ Zn²⁺+2e^-

Q18. 

(a) Name the charged particles which attract one another to form electrovalent compounds.

(b) In the formation of electrovalent compounds, electrons are transferred from one element to another. How are electrons involved in the formation of a covalent compound?

(c) The electronic configuration of nitrogen is (2, 5). How many electrons in the outer shell of nitrogen atom are not involved in the formation of a nitrogen molecule?

(d) In the formation of magnesium chloride (by direct combination between magnesium and chlorine), name the substance that is oxidized and the substance that is reduced.

Q19. What is the term defined below?

(a) A bond formed by a shared pair of electrons, each bonding atom contributing one electron to the pair.

(b) A bond formed by transfer of electron(s).

Q20. Name or state the following:

(a) An element having valency zero.

(b) Metal with valency one.

(c) Atoms of the same element differing in mass numbers.

(d) Elements having same mass number but different atomic number.

(e) Bond formed by transfer of electron(s).

(f) Ion formed by gain of electron(s).

Q21. An element X has 2 electrons in its M shell, it forms bond with an element Y which has 7 electrons in its third orbit.

(a) Write the formula of the compound formed.

(b) Which nearest inert gas electronic configuration will element X and Y acquire.

(c) Show by orbital diagram the formation of compound between X and Y.

Q22. In the formation of (i) oxygen molecule (ii) carbon tetrachloride molecule, state the following:

(a) Electronic configuration of nearest inert gas attained.

(b) How many electrons are shared/transferred in bond formation?

(c) Which type of bonds these compounds form?

(d) Draw their orbital diagrams.