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6. An atom has several subatomic particles, three of which are proton, electron, and neutron.

Chemists consider an atomic model with three of these particles is sufficient. Explain the
reason.

7. Consider the element of aluminium

a. What are the atomic number and mass number of aluminium ?
b. What is the difference between atomic number and mass number ?

c. Could another element have the same atomic number as aluminium ? Why ?
d. From the information above, can you determine the number of electrons of aluminium ?

8. Check out the two atoms of Carbon (Z= 6); C-12 and C-14.

a. Are C-12 and C-14 isotopes, isobars, or isotones ?
b. Element X has 7 protons and 7 neutrons. Does element X form a pair of isotopes, isobars,

or isotones with atom C-14 ?

9. a. Why was Rutherford’s atom considered unstable ?
b. Explain the importance of atomic spectrum in the development of Bohr’s atomic model.

Relate your explanation with Bohr’s postulates.

10. You are given three elements : Be (Z= 4), F(Z= 9), and Mg (Z= 12)

a. Write down their electron configuration

b. Determine their valence electrons
c. Which two elements have similar chemical properties ? Explain briefly.

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