Structure of molecules|Ch#4 chemistry 9th|tutoronlines

Chapter No # 4

Structure of molecules

Table of content:

Sr. No Name of Topic
1 Atoms Form Chemical
2 Chemical bonds
3 Types of chemical bound
4 Intermolecular Forces
5 Nature of Bonding and Properties
6 Ionic compounds
7 Properties of Metals
8 Ice floats on the surface of water

Give short Answer to the following Questions

Q.No.1. Explain double covalent bond with the help of an example?

Ans. A double Covalent bound is formed by the mutual sharing of two pairs of electrons. It is represent the double lines. This type of double covalent bond is Oxygen (O2) gas.

Q.No.2. Why does sodium make ionic bound with chlorine?

Ans. Sodium is an electron positive element. It’s ionization energy is very low. It has tendency to lose electron and become Na+. While Cl is an electronegative element. It has high electron affinity, so it attract the electron and become Cl-. They complete their valance shell with 8 electrons. Both ions stable themselves by electrostatic force of attraction.

Q.No.3. Which type of covalent bond is formed in N2 gas?

Ans. There is triple covalent bond is nitrogen gas.

Q.No.4. Define non polar covalent bond is formed in N2 gas?

Ans. When a covalent bond is formed between two similar atoms, the shared pair of electron are attracted by both the atoms equally, such type of bond is called non polar covalent bond.

Q.No.5. What is meant by triple covalent bond? Explain it with an example.

Ans. A type of covalent bond formed by mutual sharing of six electrons. It is represent the three short lines between two atoms. e.g Nitrogen molecules have triple covalent bond.

Q.No.6. Draw the Lewis structure diagram of Cl2?
Ans. Lewis Structure diagram:

Q.No.7. Write the electronic configuration of Cl- ion?

Ans.

Cl = 1S2, 2S2, 2P6, 3S2, 3P5

Q.No.8. What is the metallic bond?

Ans. A bond formed due to mobile electrons between metallic atoms ( positive charged ions).

Q.No.9. Why does chlorine accept an electron and attain negative one charge?

Ans. Chlorine has seven electrons in its valence shell, to complete its last orbital, it requried only one electron. So to make it stable, either it has to give up seven electron or gain one electrons. As it is easy to gain one electron, instead of releasing seven electrons, it gain one electron and attain one negative charge.

Q.No.10. Define Ionic bond with an example?

Ans. The type of chemical bond in which electron is transferred from one atom to another, called ionic bond.

Q.No.11. How many bond pairs of electrons are found in NH3 Molecule?

Ans. There are three bond pair of electrons in the molecules of NH3.

Q.No.12. Why a covalent bond becomes polar?

Ans. When there is difference of electron negativity between two bonded atom, then there is unequal attraction of bond pair between these atoms, resulting in formation of polar covalent bond.

Q.No.13. What is difference between ionic bond and covalent bond?
Ans. Ionic bond:

A type of chemical bond, which is formed by complete transfer of electron form one atoms to another.

Covalent bond:

A type of bond formed by sharing of electrons between two atoms.

Q.No.14. Point out the type of covalent bond in the following molecules. CH4, C2H4, H2, N2 and O2?

Ans. H2, CH4 = single covalent bond
O2, C2H4 = Double covalent bond
N2 = Triple covalent bond

Q.No.15. What is difference between bond pair and lone pair of electrons? Explain with an example.
Ans. Bond pair:

A pair of electron in a molecule in that take part in bonding is called bond pair.

Lone pair:

Non bonding electron pair present on atom of molecule is called lone pair.

Q.No.16. Why does oxygen molecule not form a polar covalent bond?

Ans. In oxygen molecule, there is equal sharing of bonded pair between two atoms. Due to this polar covalent bond is not formed,

Q.No.17. Differentiate between polar and non polar compounds?
Ans. Polar compound:

Those compounds which are formed by combining of different type of atoms having electronegativity difference.

Non polar compounds:

Those compounds which are formed by combining same type of atoms.

Q.No.18. Explain polar covalent bond with an example?

Ans. Covalent bond which is formed between two dissimilar atoms having a reasonable difference of electronegativities between bonded atoms is called polar covalent bond. The electronegativity difference of hydrogen and chlorine is 1.0. As chlorine has more electronegativity than hydrogen. That is why it attract the common pair of electron toward it with greater force. So due to this difference of electronegativity there is partial negative charge on chlorine and partial positive charge on hydrogen. A polarity is being developed. That is why it is known as polar covalent bond.

Q.No.19. Define hydrogen bonding?
Ans. Hydrogen bonding:

The electrostatic force of attraction between highly electronegative small atoms like oxygen nitrogen, fluorine and partial positive hydrogen atom is called hydrogen bonding. It is represented by dotted lines(……)

Q.No.20. Define the inter molecular force of attraction?

Ans. The force of attraction present between the molecules of a compound are called intermolecular forces.

Q.No.21. Why does ice float on water?

Ans. When water is cooled, it become freeze due to hydrogen bonding. The distance between water molecules increase at specific distance, resulting in the density of ice becomes less than that of water. That’s the reason why ice floats on water.

Q.No.22. What do you mean by malleability?

Ans. Malleability is a property by virtue of which it can be drawn into sheets.

Q.No.23. Metals are good conductors of electricity, why?

Ans. Metals are good conductor of electricity, because they have mobile free electrons. When electric field is applied across the metals, the free electron coming toward positive pole, got new space. This pressure of electron force the free electron to move. In this way current is passed through metal.

Q.No.24. Write any two properties of ionic compounds?

Ans. Following are the properties of ionic compounds.
1. Ionic compounds are crystalline solids.
2. In solid from there is trace of electrical conductance of ionic compound. But in solution or melted from they are good conductors of electricity.

Q.No.25. Ionic bond is stronger than covalent bond explain?

Ans. The ions of ionic compound have strong electrostatic force. Due to which they stable strongly on their positions. That is why ionic bond is more stronger than covalent bond.

Q.No.26. Ionic compounds are solids? Justify?

Ans. Ionic compounds are solids because ionic compound, have very strong ionic bonds, combine ions to give solids.

Q.No.27. Write down any four properties of metals?

Ans. Four properties of metals are following,

  1. All metals are solids except mercury.
  2. They have high melting and boiling point.
  3. They are good conductor of electricity.
  4. They have metallic bonding.

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