Q: A sample contains $$3.00$$ moles of carbon atoms. How many atoms are present in the sample?

$$1.81 \times 10$$^{24}$$ atoms

Q: The atomic mass of chlorine is $$35.45$$ amu. If chlorine consists of $$75.77\%$$ $$^{35}Cl ($$mass $$34.97$$ amu) and $$24.23\%$$ $$^{37}Cl ($$mass $$36.97$$ amu), which formula correctly calculates the atomic mass?

$$(0.7577 \times 34.97) + (0.2423 \times 36.97)$$

Q: How many atoms are present in $$12.0 g of $$carbon? (Molar mass of C = $$12.0 g/$$mol, Avogadro's number $$= 6.022 \times 10$$^{23}$$)

$$6.022 \times 10$$^{23}$$ atoms

Question 1

Which subatomic particle has a mass closest to $$1.67493 	imes 10$$^{-27}$$ kg and no electrical charge?

Accepted Answer

Neutron

Question 2

An atom of tin (Sn) contains 50 protons. What is its atomic number ($$Z$$)?

Accepted Answer

$$Z = 50$$

Question 3

Which statement best explains why isotopes of the same element have different masses?

Accepted Answer

They have different numbers of neutrons.

Question 4

A neutral atom of oxygen has 8 protons. How many electrons does the $$O^{2-}$$ ion have?

Accepted Answer

10

Question 5

Which of the following elements is classified as a metalloid and is commonly used in semiconductors?

Accepted Answer

Silicon (Si)

Question 6

Which group in the periodic table contains the most chemically stable elements?

Accepted Answer

Group 8A (noble gases)

Question 7

A sample contains $$3.00$$ moles of carbon atoms. How many atoms are present in the sample?

Accepted Answer

$$1.81 	imes 10$$^{24}$$ atoms

Question 8

Which element is a main-group metal that tends to lose two electrons to form a $$2^+$$ ion?

Accepted Answer

Calcium (Ca)

Question 9

The atomic mass of chlorine is $$35.45$$ amu. If chlorine consists of $$75.77\%$$ $$^{35}Cl ($$mass $$34.97$$ amu) and $$24.23\%$$ $$^{37}Cl ($$mass $$36.97$$ amu), which formula correctly calculates the atomic mass?

Accepted Answer

$$(0.7577 	imes 34.97) + (0.2423 	imes 36.97)$$

Question 10

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

Accepted Answer

Elements are arranged by increasing atomic number, and properties recur periodically.

Question 11

A sample of aluminum has a mass of $$54.0 g. $$How many moles of aluminum does it contain? (Molar mass of Al = $$26.98 g/$$mol)

Accepted Answer

$$2.00$$ mol

Question 12

Which element is a main-group nonmetal that tends to gain one electron to form a $$1^-$$ ion?

Accepted Answer

Chlorine (Cl)

Question 13

Which of the following best describes the difference between a cation and an anion?

Accepted Answer

A cation is positively charged due to loss of electrons; an anion is negatively charged due to gain of electrons.

Question 14

Which of the following elements is a transition metal?

Accepted Answer

Iron (Fe)

Question 15

A neon atom has 10 protons and 12 neutrons. What is its mass number ($$A$$)?

Accepted Answer

$$A = 22$$

Question 16

Which of the following is true about the size of isotopes of a given element?

Accepted Answer

All isotopes of an element have nearly the same atomic size.

Question 17

Which element is a main-group element, a metal, and is found in group 4A?

Accepted Answer

Lead (Pb)

Question 18

How many atoms are present in $$12.0 g of $$carbon? (Molar mass of C = $$12.0 g/$$mol, Avogadro's number $$= 6.022 	imes 10$$^{23}$$)

Accepted Answer

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

Question 19

Which of the following is NOT a property of metals?

Accepted Answer

Tend to gain electrons during chemical changes

Question 20

Which of the following best describes the relationship between atomic mass and molar mass?

Accepted Answer

Atomic mass (amu) is numerically equal to molar mass (g/mol) for an element.

Atoms and Elements: Structure, Classification, and the Periodic Table

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