Chemistry Examination

Choose the correct option for each of the following questions. Each question carries 1 mark.

1. The number of electrons in a neutral atom with atomic number 12 and mass number 24 is:
   A 12

   B 24

   C 36

   D 6
2. Which quantum number determines the shape of an orbital?
   A Principal quantum number (n)

   B Azimuthal quantum number (l)

   C Magnetic quantum number (m)

   D Spin quantum number (s)
3. The maximum number of electrons that can be accommodated in the M-shell (n=3) is:
   A 8

   B 18

   C 32

   D 2
4. Which of the following subshells has the highest energy?
   A 3d

   B 4s

   C 4p

   D 4f
5. According to Hund’s rule, electron pairing in orbitals of the same energy occurs:
   A Immediately after one electron occupies each orbital

   B Only after all orbitals are half-filled

   C Only after each orbital has one electron

   D Randomly without any specific order
6. The electronic configuration of Chromium (Z=24) is an exception to the Aufbau principle. Its configuration is:
   A [Ar] 4s² 3d⁴

   B [Ar] 4s¹ 3d⁵

   C [Ar] 4s² 3d⁵

   D [Ar] 4s¹ 3d⁴
7. Which of the following particles was discovered in the cathode ray experiment?
   A Proton

   B Neutron

   C Electron

   D Nucleus
8. The azimuthal quantum number for f-subshell is:
   A 0

   B 1

   C 2

   D 3
9. The total number of orbitals in the third energy level (n=3) is:
   A 3

   B 9

   C 18

   D 1
10. Isotopes of an element have the same:
    A Mass number

    B Number of neutrons

    C Atomic number

    D Physical properties

Write down short answers to the following questions.

1. Explain why the 4s subshell is filled before the 3d subshell in potassium, even though the principal quantum number of the 3d subshell is lower.
2. Which of electron, proton and neutron is deflected the most in the magnetic field? (Quick Check 2.1)
3. Why is the atomic number more fundamental than the mass number?
4. For the element aluminium (Z = 13), draw a sketch graph between the log₁₀ of the successive ionization energies (y-axis) against the number of electrons removed (x-axis) (Quick Check 2.2)
5. Define the azimuthal quantum number (l).
6. Why does the f-subshell have 7 orbitals?
7. Difference between px and pz orbitals.
8. Difference between 4s and 3d orbital in terms of energy.
9. State the Pauli Exclusion Principle.
10. Why is 4s orbital filled before 3d orbital?

Write down short answers to the following questions.

1. An atom of element X has an atomic number of 17 and a mass number of 35. Determine the number of protons, neutrons, and electrons in this atom.
2. If this element forms an ion with a charge of -1, how many protons, neutrons, and electrons will be present in the ion?
3. Differentiate between atomic emission and atomic absorption spectrum.
4. What does the principal quantum number (n) indicate?
5. Define the azimuthal quantum number (l).
6. What is the maximum number of orbitals in the p-subshell?
7. Differentiate between Azimuthal and Magnetic Quantum Numbers.
8. Differentiate between orbit and orbital.
9. How does the spin quantum number affect the number of electrons in an orbital?
10. Difference between px and pz orbitals.
11. What is meant by electronic configuration?
12. State the Pauli Exclusion Principle.
13. What does (n + l) rule represent?
14. Why does electron pairing occur only after half-filling?
15. Why can’t two electrons have the same four quantum numbers?

Write detailed answers to the following questions. (Answer any 2)