144 ❯ STEP 4. Review the Knowledge You Need to Score High
- Which of the following is the electron configura-
tion of a halogen?
(A) 1s^2 1p^6 2s^2 2p^3
(B) 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^1
(C) 1s^2 2s^2 2p^6 3s^2 3p^6 3d^3
(D) 1s^2 2s^2 2p^5 - Which of the following is a possible configura-
tion for a transition metal atom?
(A) 1s^2 1p^6 2s^2 2p^3
(B) 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^1
(C) 1s^2 2s^2 2p^6 3s^2 3p^6 3d^3
(D) 1s^2 2s^2 2p^5 - The following are some electron configurations
reported by four students. Which of the follow-
ing electron configurations is not possible?
(A) 1s^2 2s^3 2p^3
(B) 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6
(C) 1s^2 2s^2 2p^6 3s^2 3p^6 3d^3
(D) 1s^2 2s^2 2p^5 - Which of the following is a possible configura-
tion for a transition metal ion?
(A) 1s^2 1p^6 2s^2 2p^3
(B) 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^1
(C) 1s^2 2s^2 2p^6 3s^2 3p^6 3d^3
(D) 1s^2 2s^2 2p^5 - If all the electrons are present in pairs, a sub-
stance is said to be diamagnetic. If there is at least
one electron by itself in an orbital, a substance is
said to be paramagnetic. In which of the follow-
ing groups are all atoms diamagnetic?
(A) Be, O, and N
(B) Mg, Se, and Xe
(C) Kr, Be, and Zn
(D) At, Sn, and Ba - Which of the following explains why oxygen
atoms, in their ground state, are paramagnetic?
(A) Pauli exclusion principle
(B) electron shielding
(C) Hund’s rule
(D) Heisenberg uncertainty principle
13. An atomic orbital can hold no more than two
electrons; this is a consequence of which of the
following?
(A) Pauli exclusion principle
(B) electron shielding
(C) Hund’s rule
(D) Heisenberg uncertainty principle
14. Why does the 4s orbital fill before the 3d orbital
starts to fill?
(A) Pauli exclusion principle
(B) electron shielding
(C) Hund’s rule
(D) Heisenberg uncertainty principle
15. Calcium reacts with element X to form an ionic
compound. If the ground-state electron con-
figuration of X is 1s^2 2s^2 2p^4 , what is the simplest
formula for this compound?
(A) CaX
(B) CaX 2
(C) Ca 4 X 2
(D) Ca 2 X 2
16. In 1927, Clinton Davisson and Lester Germer
experimentally confirmed what was known as the
de Broglie hypothesis by observing the diffrac-
tion of electrons. This led to general acceptance
of the de Broglie equation. Which of the follow-
ing best explains the diffraction of electrons?
(A) Pauli exclusion principle
(B) Hund’s rule
(C) the wave properties of matter
(D) Heisenberg uncertainty principle