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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