$$1.47 \times 10$$^{24}$$ atoms

$$\text{Average Atomic Mass} = \sum (\text{Fractional abundance} \times \text{exact mass})$$

Question 1

Which subatomic particle determines the atomic number of an element?

Accepted Answer

Proton

Question 2

An atom of sodium has 11 protons, 12 neutrons, and 11 electrons. What is its mass number?

Accepted Answer

$$23$$

Question 3

Which group on the periodic table contains the most reactive metals?

Accepted Answer

Group 1A

Question 4

What is the average atomic mass of an element with the following isotopes: 60% $$^{63}X ($$mass = 63 amu) and 40% $$^{65}X ($$mass = 65 amu)?

Accepted Answer

$$64$$ amu

Question 5

Which of the following best describes the relationship between atomic number and chemical properties?

Accepted Answer

Elements with the same atomic number have identical chemical properties.

Question 6

How many atoms are present in 2.45 moles of copper? (Use Avogadro's number: $$6.022 	imes 10$$^{23}$$ atoms/mol)

Accepted Answer

$$1.47 	imes 10$$^{24}$$ atoms

Question 7

A pure silver ring contains $$2.80 	imes 10$$^{22}$$ silver atoms. How many moles of silver atoms does it contain?

Accepted Answer

$$0.0465$$ moles

Question 8

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 9

Calculate the number of grams in 0.90 moles of carbon. (Molar mass of carbon = $$12.01 g/$$mol)

Accepted Answer

$$10.81 g$$

Question 10

Which group on the periodic table contains the noble gases?

Accepted Answer

Group 8A

Question 11

What is the percent abundance of isotope $$^{10}B if $$the average atomic mass of boron is $$10.81$$ amu, and the only other isotope is $$^{11}B$$?

Accepted Answer

$$19\%$$

Question 12

Which of the following is the correct formula for calculating average atomic mass?

Accepted Answer

$$	ext{Average Atomic Mass} = \sum (	ext{Fractional abundance} 	imes 	ext{exact mass})$$

Question 13

If you have 5.57 grams of carbon, how many moles do you have? (Molar mass of carbon = $$12.01 g/$$mol)

Accepted Answer

$$0.464$$ moles

Question 14

Which of the following elements is most likely to form a $$+1$$ ion?

Accepted Answer

Sodium (Group 1A)

Question 15

What is Avogadro's number?

Accepted Answer

$$6.022 	imes 10$$^{23}$$

Question 16

Which of the following best explains why elements in the same group have similar chemical properties?

Accepted Answer

They have the same number of valence electrons.

Question 17

A sample contains $$1.50 	imes 10$$^{24}$$ atoms of magnesium. How many moles of magnesium are present?

Accepted Answer

$$2.49$$ moles

Question 18

Which of the following is NOT a property of noble gases?

Accepted Answer

Highly reactive

Question 19

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

Accepted Answer

Elements are arranged by increasing atomic number.

Question 20

If an atom has 10 protons, 10 neutrons, and 10 electrons, what is its atomic number and mass number?

Accepted Answer

Atomic number: $$10$$, Mass number: $$20$$

Fundamentals of Atoms, Isotopes, Atomic Mass, and the Mole

Study Guide - Practice Questions