NIOS Class 10 Chemical Bonding Worksheet 7 Answers

This post explains the answers of questions of worksheet 7 including explanation, diagrams based on Chapter 7 of NIOS class 10. These solutions will help you complete your assignments and TMA also.

NIOS Class 10 Science (212) Worksheet 7 Solutions

Q1. The element A and B have atomic number 11 and 17 respectively. They have 1 and 7 valence electrons. Based upon this information answer the following questions:

   a.  What will be the nature of these elements- metal or non- metals?

   b. Give their electronic configuration.

   c.  What is the valency of A in the molecule formed?

   d. What type of bond these will form?

Answer

 Element ‘A’ with atomic number 11 is Sodium (Na) and element ‘B’ with atomic number 17 is chlorine (Cl)

(a)       Nature of elements

   Element A (Na) – Metal

   Element B (Cl) – Non metal

(b)        Electronic configuration

  Element A(Na)- 1s² 2s² 2p⁶ 3s¹

  Element B (Cl) -1s² 2s² 2p⁶ 3s² 3p⁵

(c)       Valency of A in molecule formed

 Element a (here Na) loses 1 electron to achieve stable configuration and form compound.so valency is 1.

(d)      Type of bond formed

 Ionic bond is present in the compound NaCl

 

Q2. Give reasons why ionic compounds are soluble in water and insoluble in organic compounds.

Answer

Ionic compounds consist of positively and negatively charged ions and bonded by strong electrostatic force.

Water is a polar solvent and its molecule have partial positive charge charge `(H^(δ+))` and partial negative charge `(O^(δ-))`. These polar water molecules pull the ions of ionic compounds and break the strong ionic bond so the salt dissolves in water.

Organic solvents like benzene, ether are non- polar so they cannot break the strong electrostatic force between the ions so ionic compounds do not dissolve in them.

 

Q3. Which steps have been taken place in the formation of an ionic compound? Explain it.

Answer

Steps in the formation of an ionic compound

We will understand this through the formation of sodium chloride

    1.  Formation of cation

Metal atom loses its valence electrons and form cation.

Sodium loses 1 electron to achieve a stable configuration and forms sodium ion (Na⁺)

  Na    →  Na⁺ + e^-

(2,8,1)     (2,8)

   2. Formation of anion

 Non-metal atom gains electron and form anion. Chlorine accepts 1 electron in the outermost shell and form chloride ion (Cl^-)

  Cl   +    e^-   → Cl^-

(2,8,7)             (2,8,8)

    3. Formation of ionic lattice

 The oppositely charge ions attract each other due to strong electrostatic force ions are arranged in ionic lattice in which each cation is surrounded by anions and vice versa.

Na⁺ + Cl^- → NaCl

Q4.  “Ionic compounds have high melting point and high boiling point”. Explain it with example.

Answer

Ionic compounds have high electrostatic forces of attraction present between the opposite ions so a lot of thermal energy is required to overcome these forces. So they melt on very high temperature and after that they start boiling at more high temperature.

Example: NaCl has melting point 1074K and boiling point 1686K.

   

Q5. “Covalent compounds have generally low melting point and boiling point” Justify this statement with reasons.

Answer

Covalent compounds have low melting points because the forces of attraction between molecules is weak so a small amount of energy is required to break these weak intermolecular forces.

Example: Naphthalene is a covalent compound has melting point 353K.

 

Q6. Do you think reaction of covalent compounds generally fast? If yes, explain with reasons.

Answer

No, covalent compounds react slowly. Covalent compounds have strong covalent bond and they do not form ions so most of the covalent compounds do not react fast.

 

 

Q7. Write the Lewis dot structure of the following elements: - O₂ , HCl, MgCl₂, N₂.

Answer

 

 

Q8. Give reasons why noble gases are non-reactive. Also explain about Octet rule.

Answer

Noble gases are non-reactive - Noble gases have completely filled outermost shell so they do not gain, lose or share electrons that’s why their chemical reactivity is almost low under normal conditions. So, they are non- reactive.

Octet Rule- Atoms of elements have tendency to achieve eight electrons in their outermost shell to attain stable noble gas configuration. So, atoms lose, gains or share electrons during chemical reactions. This is octet rule.

Example

Sodium loses 1 electron form outermost shell to form Na⁺ ion and chlorin atom gains this 1 electron to form Cl^- ion. Now both achieve stable configuration and form stable compound NaCl

                         

 

Q9. How does shared pair of electrons hold the two atoms together in the covalent bond? Give reasons in support of your answer.

Answer

Two atoms share one or more pairs of electrons to achieve stable electronic configuration in their outermost shell. These shared pair of electrons are attracted by the nuclei of both atoms and form a strong covalent bond between them.

Example

 In H₂ molecule – each hydrogen atom share one electron and form single covalent bond between atoms.

 

 

Q10.Classify the following compounds into ionic and covalent compound:

    a.  Magnesium chloride

    b. Ammonia

    c.  Hydrogen chloride

    d. Calcium chloride

    e.  Magnesium oxide

    f.   Sodium chloride

    g. Methane

    h. Carbon dioxide

Answer

    a.  Magnesium chloride – Ionic compound

    b. Ammonia - Covalent compound

    c.  Hydrogen chloride - Covalent compound

    d. Calcium chloride - Ionic compound

    e.  Magnesium oxide - Ionic compound

    f.   Sodium chloride - Ionic compound

    g. Methane - Covalent compound

    h. Carbon dioxide – Covalent compound

   

   This is the complete solutions of worksheet of Chemical Bonding. This will help you secure good grade in NIOS Class 10 Examinations.