Q: Calculate the atomic weight of chlorine given that $$^{35}\mathrm{Cl} ($$atomic mass = 34.969 amu) is 75.78% abundant and $$^{37}\mathrm{Cl} ($$atomic mass = 36.966 amu) is 24.22% abundant.

$$(0.7578 \times 34.969) + (0.2422 \times 36.966) = 35.45$$ amu

Q: How many atoms are present in 2.00 moles of helium?

$$2.00 \times 6.022 \times 10$$^{23}$$ = 1.20 \times 10$$^{24}$$ atoms

Q: How many iron atoms are in a 4.50 g pure iron nail? (Atomic mass of Fe = 55.85 g/mol, Avogadro’s number = $$6.022 \times 10$$^{23}$$)

$$\frac{4.50}{55.85} \times 6.022 \times 10$$^{23}$$ = 4.85 \times 10$$^{22}$$ atoms

Q: Which of the following best describes the relationship between atomic mass unit (amu) and grams?

$$1 \text{ amu} = 1.66054 \times 10$$^{-24}$$ \text{ g}$$

Question 1

Which statement best describes the modern atomic theory?

Accepted Answer

Atoms of each element have the same number of protons, but may have different numbers of neutrons.

Question 2

Which subatomic particle is responsible for the chemical properties of an element?

Accepted Answer

Electron

Question 3

A neutral atom of magnesium has an atomic number of 12 and a mass number of 24. How many neutrons does it contain?

Accepted Answer

$$24 - 12 = 12$$ neutrons

Question 4

Which of the following best explains why atoms are electrically neutral?

Accepted Answer

They have equal numbers of protons and electrons.

Question 5

Which of the following is a correct representation of an isotope of sodium with 11 protons, 12 neutrons, and 10 electrons?

Accepted Answer

$$^{23}_{11}\mathrm{Na}^{+}$$

Question 6

Which of the following elements is a transition metal?

Accepted Answer

Iron (Fe)

Question 7

What is the charge on an ion formed when a chlorine atom gains one electron?

Accepted Answer

$$1-$$

Question 8

Which of the following best describes a cation?

Accepted Answer

A positively charged ion formed by losing electrons

Question 9

Which group in the periodic table contains the noble gases?

Accepted Answer

Group 8A

Question 10

Calculate the atomic weight of chlorine given that $$^{35}\mathrm{Cl} ($$atomic mass = 34.969 amu) is 75.78% abundant and $$^{37}\mathrm{Cl} ($$atomic mass = 36.966 amu) is 24.22% abundant.

Accepted Answer

$$(0.7578 	imes 34.969) + (0.2422 	imes 36.966) = 35.45$$ amu

Question 11

How many atoms are present in 2.00 moles of helium?

Accepted Answer

$$2.00 	imes 6.022 	imes 10$$^{23}$$ = 1.20 	imes 10$$^{24}$$ atoms

Question 12

A pure copper wire has a mass of 12.7 g. How many moles of copper does it contain? (Atomic mass of Cu = 63.55 g/mol)

Accepted Answer

$$\frac{12.7}{63.55} = 0.200$$ mol

Question 13

How many iron atoms are in a 4.50 g pure iron nail? (Atomic mass of Fe = 55.85 g/mol, Avogadro’s number = $$6.022 	imes 10$$^{23}$$)

Accepted Answer

$$\frac{4.50}{55.85} 	imes 6.022 	imes 10$$^{23}$$ = 4.85 	imes 10$$^{22}$$ atoms

Question 14

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 15

Which of the following is the correct order of increasing number of neutrons for the isotopes: barium-133, iodine-131, strontium-90, uranium-238?

Accepted Answer

Strontium-90 \u003c Iodine-131 \u003c Barium-133 \u003c Uranium-238

Question 16

Which of the following best describes the relationship between atomic mass unit (amu) and grams?

Accepted Answer

$$1 	ext{ amu} = 1.66054 	imes 10$$^{-24}$$ 	ext{ g}$$

Question 17

Which of the following elements is most likely to form a $$2+$$ ion?

Accepted Answer

Magnesium (Mg)

Question 18

A sample contains $$3.01 	imes 10$$^{23}$$ atoms of silver (Ag). How many moles of silver are present?

Accepted Answer

$$\frac{3.01 	imes 10$$^{23}$$}{6.022 	imes 10$$^{23}$$} = 0.500$$ mol

Atoms and Elements: Foundations of Atomic Structure and the Periodic Table

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