Q: Which of the following is the correct relationship for calculating the atomic mass of an element with multiple isotopes?

$$\text{Atomic mass} = \sum (\text{fraction of isotope} \times \text{mass of isotope})$$

Q: A sample contains 15.66 g of aluminum. Given that the molar mass of aluminum is 26.98 g/mol, how many atoms of aluminum are present in the sample? ($$1\ \text{mol} = 6.022 \times 10$$^{23}$$ atoms)

$$3.49 \times 10$$^{23}$$ atoms

Q: Which of the following is the correct conversion factor to use when converting from moles of atoms to number of atoms?

$$6.022 \times 10$$^{23}$$\ \text{atoms} / 1\ \text{mol}$$

Question 1

Which of the following statements is NOT part of Dalton's Atomic Theory?

Accepted Answer

Atoms of one element can change into atoms of another element during a chemical reaction.

Question 2

J.J. Thomson's cathode ray tube experiment led to the discovery of which subatomic particle, and what property did he measure?

Accepted Answer

The electron; charge-to-mass ratio

Question 3

Which of the following best describes the result of Rutherford's gold foil experiment?

Accepted Answer

Most alpha particles passed through, but a few were deflected at large angles, indicating a small, dense nucleus.

Question 4

Which of the following is the correct relationship for calculating the atomic mass of an element with multiple isotopes?

Accepted Answer

$$	ext{Atomic mass} = \sum (	ext{fraction of isotope} 	imes 	ext{mass of isotope})$$

Question 5

A sample contains 15.66 g of aluminum. Given that the molar mass of aluminum is 26.98 g/mol, how many atoms of aluminum are present in the sample? ($$1\ 	ext{mol} = 6.022 	imes 10$$^{23}$$ atoms)

Accepted Answer

$$3.49 	imes 10$$^{23}$$ atoms

Question 6

Which of the following elements is a metalloid and is commonly used as a semiconductor due to its intermediate electrical conductivity?

Accepted Answer

Silicon

Question 7

Which group in the periodic table contains elements that are all gases at room temperature and are mostly unreactive?

Accepted Answer

Group 8A (Noble gases)

Question 8

A certain element has two naturally occurring isotopes: isotope A with a mass of 10.01 amu and 80% abundance, and isotope B with a mass of 11.01 amu and 20% abundance. What is the atomic mass of the element?

Accepted Answer

$$10.21\ 	ext{amu}$$

Question 9

Which of the following statements about ions is correct?

Accepted Answer

Cations are positively charged ions formed when atoms lose electrons.

Question 10

Which of the following best explains why the atomic mass of chlorine is not a whole number?

Accepted Answer

Chlorine exists as a mixture of isotopes with different masses and natural abundances.

Question 11

Which of the following is the correct symbol for an isotope of neon with 10 protons and 12 neutrons?

Accepted Answer

$$^{22}	ext{Ne}$$

Question 12

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

Accepted Answer

Magnesium

Question 13

A main-group element forms an anion with a predictable charge. If the element is in group 6A, what is the charge on its anion?

Accepted Answer

$$2-$$

Question 14

Which of the following is a property of metals?

Accepted Answer

They are good conductors of heat and electricity.

Question 15

How many moles of carbon are present in a 24.02 g sample of carbon? (Atomic mass of C = 12.01 g/mol)

Accepted Answer

$$2.00$$ mol

Question 16

Which of the following best describes the difference between isotopes of the same element?

Accepted Answer

They have the same number of protons but different numbers of neutrons.

Question 17

Which of the following is the correct conversion factor to use when converting from moles of atoms to number of atoms?

Accepted Answer

$$6.022 	imes 10$$^{23}$$\ 	ext{atoms} / 1\ 	ext{mol}$$

Question 18

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

Accepted Answer

They have a full outer shell of electrons, making them stable.

Question 19

Which of the following statements about the periodic table is correct?

Accepted Answer

Elements in the same group have similar chemical properties.

Atoms and Elements: Foundations of Atomic Theory and Structure

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