Q: A photon is emitted when an electron in a hydrogen atom transitions from $n=4$ to $n=2$. Which equation gives the energy of the emitted photon?

$E = -2.18 \times 10^{-18} \left( \frac{1}{2^2} - \frac{1}{4^2} \right)\ \text{J}$

Q: Which of the following best describes the periodic trend for atomic radius?

Atomic radius decreases across a period and increases down a group.

Q: Which of the following is the correct Lewis structure for carbon dioxide ($\text{CO}_2$)?

O=C=O, with each O atom having two lone pairs.

Question 1

Which of the following best describes the quantum numbers for the 3p electron in a sodium atom?

Accepted Answer

$n = 3, \ l = 1, \ m_l = 0, \ m_s = +\frac{1}{2}$

Question 2

Which of the following electron configurations represents a ground state atom of sulfur (S)?

Accepted Answer

$1s^2\ 2s^2\ 2p^6\ 3s^2\ 3p^4$

Question 3

A photon is emitted when an electron in a hydrogen atom transitions from $n=4$ to $n=2$. Which equation gives the energy of the emitted photon?

Accepted Answer

$E = -2.18 	imes 10^{-18} \left( \frac{1}{2^2} - \frac{1}{4^2} ight)\ 	ext{J}$

Question 4

Which of the following elements has the highest effective nuclear charge ($Z_{	ext{eff}}$) for its valence electrons?

Accepted Answer

Fluorine

Question 5

Which of the following best explains why atomic radius decreases across a period from left to right?

Accepted Answer

Increasing effective nuclear charge pulls electrons closer to the nucleus.

Question 6

Which of the following pairs of elements is most likely to form an ionic bond?

Accepted Answer

Sodium and Chlorine

Question 7

Which of the following statements about periodic trends is correct?

Accepted Answer

Ionization energy increases across a period and decreases down a group.

Question 8

Which of the following orbital diagrams correctly represents the ground state of nitrogen ($Z=7$)?

Accepted Answer

Three unpaired electrons in the $2p$ orbitals, each with parallel spins.

Question 9

Which of the following best describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons; covalent bonds involve the sharing of electrons.

Question 10

Which of the following is the correct electron configuration for a $	ext{Cl}^-$ ion?

Accepted Answer

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

Question 11

A sample of neon gas is excited in a discharge tube, and the emission spectrum is observed. Which principle explains the appearance of discrete lines in the spectrum?

Accepted Answer

Electrons in neon atoms occupy quantized energy levels.

Question 12

Which of the following best explains why magnesium forms a $2+$ ion?

Accepted Answer

It loses two electrons to achieve a noble gas configuration.

Question 13

Which of the following is the correct order of increasing electronegativity?

Accepted Answer

Na < Mg < Cl < F

Question 14

Which of the following best describes the periodic trend for atomic radius?

Accepted Answer

Atomic radius decreases across a period and increases down a group.

Question 15

Which of the following is the correct Lewis structure for carbon dioxide ($	ext{CO}_2$)?

Accepted Answer

O=C=O, with each O atom having two lone pairs.

Question 16

Which of the following best explains why the first ionization energy of sodium is lower than that of magnesium?

Accepted Answer

Sodium has a lower effective nuclear charge than magnesium.

Question 17

Which of the following is the correct set of quantum numbers for the last electron added to a phosphorus atom ($Z=15$)?

Accepted Answer

$n=3,\ l=1,\ m_l=1,\ m_s=+\frac{1}{2}$

Question 18

Which of the following best describes the process that occurs when sodium reacts with chlorine to form table salt?

Accepted Answer

Sodium loses an electron and chlorine gains an electron, forming $	ext{Na}^+$ and $	ext{Cl}^-$ ions.

Question 19

Which of the following best explains why noble gases are generally unreactive?

Accepted Answer

They have completely filled valence shells.

Question 20

Which of the following is the correct electron configuration for a calcium ion ($	ext{Ca}^{2+}$)?

Accepted Answer

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

General Chemistry: Atomic Structure, Periodicity, and Bonding – Study Guide

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