Review Questions

1. State the postulates of Dalton's atomic theory

2. Define the following terms: (a) α-particle, (b) β-particles, (c) γ ray (d) X Ray.

3. Compare the properties of the following : α-particle, cathode rays, protons, neutrons, electrons.

4. Describe the experimental basis for believing that the nucleus occupies a very small fraction of the volume of the atom.

5. Define the following terms: (a) atomic number, (b) mass number

Why does knowledge of atomic number enable us to deduce that number of electrons present in an atom?

6. Explain the meaning of each term in the symbol? _Z^AX

7, Indicate the number of protons, neutrons, and electrons in each of the following species:

₇¹⁵N, ₁₆³³S, ₂₉⁶³Cu, ₃₈⁸⁴Sr, ₅₆¹³⁰Ba, ₇₄¹⁸⁶W, ₈₀²⁰²Hg

8. For the noble gases (the group 8A elements).

₂⁴He, ₁₀²⁰Ne, ₁₈⁴⁰Ar, ₃₆⁸⁴Kr, ₅₄¹³²Xe

(a) Determine the number of protons and neutrons In the nucleus o; each atom and
(b) Determine the ratio of neutrons to protons in the nucleus each atom. Describe any general trend you discover in the wad this ratio changes with increasing atomic number.

9. Write the appropriate symbol for each of the following isotopes

(a) Z = 1, A = 23; (b) Z = 28, A = 64; (c) Z = 74; A = 186; (d) Z = 80, A = 201.

10. Which of the following symbols provides us with more information about the atom: ²³Na or ₁₁Na? Explain

11. The atomic masses of ₁₇³⁵Cl (75.53%) ₁₇^35ACl and (24.47%) are 34.968 amu and 36.956 amu, respectively. Calculate the average atomic mass of chlorine. The percentages in parentheses denote the relative abundances.

12. The atomic masses of ₃⁶Li and ₃⁷Li are 6.0151 amu and 7.0160 amu respectively, calculate the natural abundances of these two isotopes. The average atomic mass of Li is 6.941 amu.

13. Arrange the following in order of increasing mass (a) 16 water molecules (b) 2 atoms of lead, (c) 5.1 x 10^-23 mole of helium.

15. A 4.25g sample of compound contains only carbon, hydrogen, and oxygen was burnt in an atmosphere of pure O₂. This produced 9.34 g CO₂ and 5.09g H₂O.

(a) Calculate the masses of C and H that were in the original 4.25g.
(b) What was the mass of 0 in the original sample?
(c) What is the percentage composition of this compound?
(d) What is the empirical formula of the compound described?

16. Allicin is the compound responsible for the characteristic smell of garlic. An analysis of the compound gives the following percent composition by mass: C: 44.4%; H: 6.21 %; S: 39.5%; 0: 9.86%.

Calculate its empirical formula. What is its molecular formula given that its molar mass is about 162g?