Directions: Choose and encircle the letter of the correct answer.

1. How does the mass number of an atom be obtained?
a. by adding the protons and the electrons
b. by adding the electrons and the neutrons
c. by determining the number of protons only
d. by adding the number of protons and neutrons

2. Where does the entire mass of an atom concentrated?
a. protons b. neutrons c. electrons d. nucleus

3. How are structures like protons, electrons and neutrons being called? a. sub-atomic particles b. nucleons c. atomic number d. nucleus

4. Which among these elements has an atomic number of 15?
a. Lithium b. Phosphorus c. Calcium d. Magnesium

5. An element has a mass number of 35 and an atomic number of 17. How many neutrons does this atom have?
a. 18 b. 17 c. 35 d. 52

6. Which among the sub-atomic particles of an atom is negatively charged?
a. proton b. neutron c. electron d. nucleus

7. Which of the following elements has an atomic number of 20?
a. Calcium b. Oxygen c. Sodium d. Phosphorus

8. How do you determine the identity of an element?
a. by the number of its neutron
b. by the number of its proton
c. by the number of its electron
d. by its mass number

9. What happens when an atom gains electron?
a. It becomes positively charge.
b. It becomes neutral.
c. It becomes negatively charge.
d. No changes take place.

10. What is an isotope?
a. Atoms of the same element with different mass numbers.
b. Atoms of the same element with different proton numbers.
c. Atoms of the same element with different electron numbers.
d. Atoms of the same element with different atomic numbers. ​