Question 1

Which statement best describes a key difference between Dalton’s atomic theory and the modern atomic theory?

Accepted Answer

Dalton’s theory proposed that atoms are indivisible, while modern theory recognizes the existence of subatomic particles.

Question 2

Given the atomic notation $^{23}_{11}Na$, what is the number of neutrons in this sodium atom?

Accepted Answer

12

Question 3

Which of the following elements is classified as a metalloid?

Accepted Answer

Silicon (Si)

Question 4

Which periodic trend increases from left to right across a period and decreases down a group?

Accepted Answer

Electronegativity

Question 5

What is the electronic configuration of a nitrogen atom ($Z=7$) in terms of shells?

Accepted Answer

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

Question 6

Which of the following best explains the stability of noble gases?

Accepted Answer

They have completely filled valence electron shells.

Question 7

Which of the following ions has the formula $\mathrm{SO_4^{2-}}$?

Accepted Answer

Sulfate

Question 8

Which process requires more energy: removing an electron from a noble gas or from an alkali metal? Why?

Accepted Answer

Removing an electron from a noble gas requires more energy because noble gases have full valence shells and high ionization energies.

Question 9

Which of the following is a characteristic of ionic bonds?

Accepted Answer

They result from the transfer of electrons from one atom to another.

Question 10

What is the Lewis structure for water ($\mathrm{H_2O}$)?

Accepted Answer

O atom in the center with two single bonds to H atoms and two lone pairs on O.

Question 11

A sample contains $3.01 	imes 10^{23}$ molecules of carbon dioxide. How many moles of carbon dioxide are present?

Accepted Answer

$0.5$ mol

Question 12

Calculate the molar mass of $\mathrm{Ca(OH)_2}$.

Accepted Answer

$74\ \mathrm{g\ mol^{-1}}$

Question 13

A compound contains 40% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula?

Accepted Answer

$\mathrm{CH_2O}$

Question 14

Which law states that mass is neither created nor destroyed in a chemical reaction?

Accepted Answer

Law of Conservation of Mass

Question 15

Balance the following chemical equation: $\mathrm{C_2H_6 + O_2 \rightarrow CO_2 + H_2O}$

Accepted Answer

$2\mathrm{C_2H_6} + 7\mathrm{O_2} \rightarrow 4\mathrm{CO_2} + 6\mathrm{H_2O}$

Question 16

How many moles of $\mathrm{NaCl}$ are present in $117$ g of $\mathrm{NaCl}$? ($\mathrm{Na} = 23$, $\mathrm{Cl} = 35.5$)

Accepted Answer

$2$ mol

Question 17

Which of the following best describes metallic bonding?

Accepted Answer

A lattice of positive ions surrounded by a sea of delocalized electrons.

Question 18

Which element has the highest first ionization energy?

Accepted Answer

Helium

Question 19

A patient is given $18$ g of glucose ($\mathrm{C_6H_{12}O_6}$) intravenously. How many moles of glucose did the patient receive? ($\mathrm{C} = 12$, $\mathrm{H} = 1$, $\mathrm{O} = 16$)

Accepted Answer

$0.1$ mol

Question 20

Which of the following statements about electron affinity is correct?

Accepted Answer

Electron affinity generally becomes more negative across a period from left to right.

Atomic Structure, Periodic Classification, Chemical Bonding, and Chemical Equations

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