Model Questions and Answers STD IX Chemistry

1. Who discovered neutrons?

(J.J Thomson, Earnest Rutherford, James Chadwick, Neils Bohr)

2. Identify the relationship in the first pair and fill in the blanks in the second pair.

Electronegativity scale: Linus Pauling

Electron dot diagram…………..

3. Name the gas produced when sodium reacts with water.

(Oxygen, Hydrogen, Chlorine, Carbon dioxide)

4. Which one of the following is a fundamental particle?

(Proton, Electron, Neutron, Alpha particle)

5. What is the total number of groups in the modern periodic table?

(18, 32, 6, 7)

Answers

1.James Chadwick

2. Newton Lewis

3. Hydrogen

4. Electron

5. 18

Questions

6. Find out the wrong statements from those given below and correct them.

a)Transition elements show the properties of both metals and non-metals.

b) The size of atoms increases down the group in the periodic table.

c) The mass of atoms mainly depends upon the masses of neutrons and electrons.

d) The size of atoms decreases across a period in the periodic table.

7. Find out the oxidation number of phosphorus in the compounds given below) Hint. Oxidation number O= -2, H= +1

a) P2O5

b) H₃PO₄

8.The electron configuration of certain elements is given in the table. (Symbols are not real).

A-2,8,1

B-2,8,8

C-2,8,8,1

a) Which of these belong to the same period?

b) Which of these belong to the same group?

c) Which of these elements is more stable why?

9. Illustrate the formation of sodium fluoride using an electron-dot diagram. Hint: atomic number Na = 11 F=9

10.Match these given in Columns A and B Suitably

Column A

Gains electrons

Loses electrons

Shares electrons

Neither gains nor loses electrons

Column B

Noble gas

Covalent bonding

Oxidation

Reduction

Answer

6.a) Metalloids show the properties of both metals and non-metals.

c) The mass of atoms mainly depends on the masses of neutrons and protons.

7. a) P₂O5

2P+ -2×5=0

2P+ -10=0

2P = +10

P = +10/2 = +5)

b) H₃PO₄

(+1×3) +P+(-2×4)= 0

+3+P+-8=0

P+-5=0

P = +5

8. a) Same period: A and B

b) Same group: A and C

c) B is more stable. Because it has stable octet electron configuration in the outermost shell.

9.Na +F:→[Na]*+ [F]

2,8,1 2,7 2,8 2,8

Sodium Flourine

Sodium Flourine

10. Gains electrons – Redution

Loses electrons – Oxidation

Shares electrons – Covalent bonding

Neither gains nor loses electrons – Noble gases