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C. N- 15 has fewer electrons than N-14

D. Both have different numbers of nucleons
E. None are correct

7. All statements related Bohr‟s atomic model are not true, expect ….
A. Electron circles the nucleus in a nonstationary orbit.

B. Electron can move from one orbit to another without emitted or absorbing energy.
C. Orbit with a quantum number n = 4 refers to shell N.

D. Hydrogen atom with 1 electron has only one orbit.

E. The concept of orbit was based on the fact that atom has a continuous spectrum

8. The electron configuration of atom of potassium (Z= 19) is ….

A. 2, 8, 8, 1

B. 2, 16, 1

C. 2, 8, 9
D. 10, 8, 1

E. 2, 8, 2, 2, 7
9.The number of valence electron of an element having a mass number of 80 and 45 neutron is

….
A. 3

B. 4

C. 5
D. 6

E. 7
10. Atom of another element that has similar chemical properties with atom 16 X is ….

A. 15 A
B. 18 B

C. 19 C

D. 9 D
E. 8 E

B. Essays

1.a. The atomic concept was introduced by Democritus around 2500 years ago. Explain the
concept and point out why it wasn‟t considered scientific at that time.

b. Why was Dalton‟s atomic theory already considered scientific ?
2. How did J.J. Thomson prove that atom is not the smallest particle of matter, and come up with

his atomic model to replace Dalton‟s Model ?
3. What caused Thomson‟s Atomic Model to be replaced by Rutherford‟s Model ?

4. Why does Rutherford‟s Atomic Model use the term „positive charge‟ instead of „proton‟ ?

5. Explain how the discovery of neutron plays a role in the development of atomic structure.

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