1. Fill in the blanks:

Name	Symbol	No. of protons	No. of neutrons	Electronic configuration
Hydrogen

2. Give reasons:

1. The atom is electrically neutral.

………………………………………………………………………………………………………………………………………………………………………………………………………….

2. The mass number is greater than the atomic number.

…………………………………………………………………………………………………………………………………………………………………………………………………………

3. The 3^rd energy level in the atom contains 18 electrons.

………………………………………………………………………………………………………………………………………………………………………………………………………….

4. The equation 2n² isn’t applied to the 4^th energy level.

………………………………………………………………………………………………………………………………………………………………………………………………………….

5. ₁₀Ne doesn’t go into chemical reactions.

……………………………………………………………………………………………………………………………………………………………………………………………………….

6. The mass of the atom is concentrated in the nucleus.

………………………………………………………………………………………………………………………………………………………………………………………………………….

3. Write the scientific term:

The number of protons in the atom.
The sum of no. of protons & neutrons in the nucleus.
The basic unit of matter that takes part in a chemical reaction.
Negatively charged particles that revolves around the nucleus.

4. Choose the right answer:

1. The second energy level in ₇N contains………….electrons.

(2 – 3 – 5)

2. The chemical activity of the element depends on the number of …………………….

(electrons in the outer level – protons – neutrons )

3. All the following elements are chemically active except…………………

(₁H – ₆C – ₁₈Ar)

5. Figure………………………is an excited atom while, figure…………………is for the atom in the ground state.

6

2

1

5

2

Figure A Figure B

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