21. The shape of an s orbital is:

a) Spherical
b) Dumbbell-shaped
c) Double dumbbell-shaped
d) Complex
Answer: a) Spherical

22. The shape of a p orbital is:

a) Spherical
b) Dumbbell-shaped
c) Double dumbbell-shaped
d) Complex
Answer: b) Dumbbell-shaped

23. Which of the following represents the correct electron configuration for the element with atomic number 15 (Phosphorus)?

a) 1s² 2s² 2p⁶ 3s² 3p³
b) 1s² 2s² 2p⁶ 3s² 3p²
c) 1s² 2s² 2p⁶ 3s² 3p⁴
d) 1s² 2s² 2p⁶ 3s² 3p⁵
Answer: a) 1s² 2s² 2p⁶ 3s² 3p³

24. The maximum number of electrons that can be held in the third shell of an atom is:

a) 8
b) 18
c) 32
d) 2
Answer: b) 18

25. The term used to describe the arrangement of electrons in the orbitals of an atom is:

a) Orbital configuration
b) Atomic number
c) Isotopic distribution
d) Nuclear arrangement
Answer: a) Orbital configuration

26. Which of the following elements has an electron configuration ending in 4s² 3d¹⁰ 4p⁵?

a) Chlorine
b) Argon
c) Bromine
d) Iodine
Answer: d) Iodine

27. What is the atomic number of the element with the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶?

a) 10
b) 12
c) 18
d) 20
Answer: c) 18

28. The periodic table is arranged by increasing:

a) Atomic mass
b) Mass number
c) Atomic number
d) Neutron number
Answer: c) Atomic number

29. The elements in the same group of the periodic table have:

a) Similar atomic numbers
b) Similar atomic masses
c) Similar chemical properties
d) Different chemical properties
Answer: c) Similar chemical properties

30. Which of the following is a characteristic of transition metals?

a) They are highly reactive nonmetals
b) They have incomplete d orbitals
c) They form ions with a fixed charge
d) They are only found in liquid form
Answer: b) They have incomplete d orbitals