Atomic Structure and Bonding

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1. A sample of element X contains two isotopes, X-35 and X-37, in a ratio of 3:1 by number of atoms. What is the relative atomic mass of element X?

   1. A 36.0
   2. B 35.5
   3. C 35.0
   4. D 37.0

2. An ion of an element has a mass number of 40 and contains 18 electrons. If the ion carries a charge of 2+, how many neutrons are present in the nucleus?

   1. A 20
   2. B 18
   3. C 22
   4. D 38

3. Which of the following statements correctly explains why the first ionisation energy of sodium is lower than that of magnesium?

   1. A Sodium has a larger atomic radius which shields the nucleus more effectively.
   2. B Magnesium has more electron shells than sodium.
   3. C Magnesium has a higher nuclear charge which attracts the valence electrons more strongly.
   4. D Sodium is a non-metal while magnesium is a metal.

4. A neutral atom of an element X has a mass number of 35 and contains 18 neutrons. What is the electronic configuration of the ion formed when X gains one electron?

   1. A 1s2 2s2 2p6 3s2 3p5
   2. B 1s2 2s2 2p6 3s2 3p6 4s1
   3. C 1s2 2s2 2p6 3s1 3p6
   4. D 1s2 2s2 2p6 3s2 3p6

5. The relative atomic mass of an element Y is 24.3. Isotope A has a mass number of 24 and an abundance of 78.9%. Isotope B has a mass number of 25. What is the percentage abundance of Isotope B?

   1. A 78.9%
   2. B 12.5%
   3. C 25.0%
   4. D 21.1%

6. An atom of an element X has a mass number of 35 and an atomic number of 17. How many neutrons are present in the nucleus of this atom?

   1. A 17
   2. B 35
   3. C 52
   4. D 18

8. Chlorine has two stable isotopes: Cl-35 (75.77% abundance) and Cl-37 (24.23% abundance). Calculate the relative atomic mass of chlorine to two decimal places.

   1. A 36.00
   2. B 35.48
   3. C 35.00
   4. D 37.00

9. The electron configuration of an element Y is 2, 8, 7. Which statement correctly describes the chemical property of Y based on this configuration?

   1. A It forms a positive ion with a charge of 1+
   2. B It is a noble gas and does not react
   3. C It forms a positive ion with a charge of 3+
   4. D It forms a negative ion with a charge of 1-

10. Which of the following statements correctly describes the shape and orientation of a p orbital?

    1. A Spherical and concentric
    2. B Dumbbell-shaped and mutually perpendicular
    3. C Dumbbell-shaped and overlapping at the nucleus
    4. D Four-lobed and planar

11. The electronic configuration of an element is 1s2 2s2 2p6 3s2 3p4. Which of the following best describes the type of bond it is most likely to form with a metal element?

    1. A Covalent bond by sharing four electrons
    2. B Ionic bond by gaining two electrons
    3. C Metallic bond by delocalising electrons
    4. D Ionic bond by losing two electrons

12. An isotope of chlorine is represented as $^{35}_{17}\text{Cl}$. Which of the following correctly states the number of protons, neutrons, and electrons in a neutral atom of this isotope?

    1. A 17 protons, 17 neutrons, 18 electrons
    2. B 17 protons, 18 neutrons, 17 electrons
    3. C 18 protons, 17 neutrons, 17 electrons
    4. D 17 protons, 18 neutrons, 18 electrons

13. The relative atomic mass of an element is calculated from the abundance of its isotopes. If an element has two isotopes, $^{69}\text{X}$ (70% abundance) and $^{71}\text{X}$ (30% abundance), what is the relative atomic mass of the element?

    1. A 70.0
    2. B 69.6
    3. C 69.0
    4. D 70.6

15. Which of the following pairs of elements is most likely to form an electrovalent (ionic) bond?

    1. A Carbon and Hydrogen
    2. B Sodium and Potassium
    3. C Sodium and Chlorine
    4. D Oxygen and Fluorine

16. The relative atomic mass of an element X is 35.5. Isotope A has a mass number of 35 and an abundance of 75%, while Isotope B has a mass number of 37. What is the percentage abundance of Isotope B?

    1. A 75%
    2. B 50%
    3. C 25%
    4. D 15%

17. The isotope of carbon, C-14, is used in radiocarbon dating. Given that the relative atomic mass of the most abundant isotope, C-12, is exactly 12.000, and C-14 has a mass of 14.003, how many neutrons are present in the nucleus of a C-14 atom?

    1. A 6
    2. B 14
    3. C 20
    4. D 8

18. Consider the molecules methane (CH4) and ammonia (NH3). Both central atoms (Carbon and Nitrogen) are in Period 2. Which statement correctly describes the difference in their molecular shapes and bond angles?

    1. A CH4 is linear and NH3 is bent.
    2. B Both molecules are tetrahedral, but NH3 has a larger bond angle due to the lone pair.
    3. C CH4 is pyramidal and NH3 is tetrahedral.
    4. D CH4 is tetrahedral with a bond angle of 109.5 degrees, while NH3 is pyramidal with a bond angle of approximately 107 degrees.

19. A sample of an element X consists of two isotopes: X-20 (mass number 20) and X-22 (mass number 22). The relative atomic mass of element X is 20.8. What is the percentage abundance of the isotope X-22?

    1. A 20%
    2. B 40%
    3. C 60%
    4. D 80%

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