AP Chemistry: 1.5 Atomic Structure and Electron Configuration

AP PhysicsAP Calculus AP ChemistryAP Biology

Question

$1s^2 2s^2 2p^6 3s^2 3p^6$

How many unpaired electrons are in the atom represented by the electron configuration above?

0

B $1$

C $2$

D $3$

▶️Answer/Explanation

Ans: A The $1 s, 2 s, 2 p, 3 s$ and $3 p$ orbitals are all full, and all the electrons are paired.

Question

Which of the following represents the electron configuration of an oxygen atom in the ground state?

▶️Answer/Explanation

Ans:C This configuration contains eight electrons. According to Hund’s rule, each orbital in the last subshell to have electrons placed in it (in this case the $2 p$ subshell) has one electron placed in it before pairing of electrons in orbitals occurs.

Question

Which of the following is the correct electron configuration for a ground-state atom of magnesium (atomic number 12) ?

A $1s^22s^22p^8$

B $1s^22s^23s^23p^6$

C $1s^22s^22p^63s^2$

D $1s^22s^23s^43p^4$

▶️Answer/Explanation

Ans: C This electron configuration has the proper sequence of orbitals filled with the correct number of electrons.

Question

The charge on an electron was determined in the __________.
A) Rutherford gold foil experiment
B) Dalton atomic theory
C) cathode ray tube, by J. J. Thompson
D) atomic theory of matter
E) Millikan oil drop experiment

▶️Answer/Explanation

Ans: E

AP Chemistry: 1.5 Atomic Structure and Electron Configuration – Exam Style questions with Answer- MCQ

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