Q: What is the charge-to-mass ratio of the electron as determined by J.J. Thomson?

$$\dfrac{e}{m} = 1.76 \times 10^8$ \ \mathrm{C/g}$$

Q: A sample contains 24.0 g of carbon. How many atoms of carbon are present in the sample? (Atomic mass of C = 12.01 g/mol, Avogadro's number $$= 6.022 \times 10$$^{23}$$)

$$\dfrac{24.0 \ \mathrm{g}}{12.01 \ \mathrm{g/mol}} \times 6.022 \times 10$$^{23}$$ = 1.20 \times 10$$^{24}$$ atoms

Q: What is the main conclusion from Millikan's oil drop experiment?

Electrons have a quantized charge of $$-1.6 \times 10$$^{-19}$$ C.

Q: What is the molar mass of helium, and how many atoms are in 8.006 g of helium?

Molar mass = 4.003 g/mol; $$\dfrac{8.006}{4.003} \times 6.022 \times 10$$^{23}$$ = 1.204 \times 10$$^{24}$$ atoms

Question 1

Which experiment provided direct evidence for the existence of the atomic nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 2

According to the Law of Multiple Proportions, if 1 g of carbon combines with 2.67 g of oxygen to form carbon dioxide and with 1.33 g of oxygen to form carbon monoxide, what is the ratio of the masses of oxygen that combine with 1 g of carbon in these two compounds?

Accepted Answer

$$\dfrac{2.67}{1.33} = 2$$

Question 3

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

Accepted Answer

They have different numbers of neutrons.

Question 4

What is the charge-to-mass ratio of the electron as determined by J.J. Thomson?

Accepted Answer

$$\dfrac{e}{m} = 1.76 	imes 10^8$ \ \mathrm{C/g}$$

Question 5

Which property is NOT characteristic of metals?

Accepted Answer

Tend to gain electrons during chemical changes

Question 6

A sample contains 24.0 g of carbon. How many atoms of carbon are present in the sample? (Atomic mass of C = 12.01 g/mol, Avogadro's number $$= 6.022 	imes 10$$^{23}$$)

Accepted Answer

$$\dfrac{24.0 \ \mathrm{g}}{12.01 \ \mathrm{g/mol}} 	imes 6.022 	imes 10$$^{23}$$ = 1.20 	imes 10$$^{24}$$ atoms

Question 7

Which of the following elements is a noble gas?

Accepted Answer

Argon

Question 8

What is the main conclusion from Millikan's oil drop experiment?

Accepted Answer

Electrons have a quantized charge of $$-1.6 	imes 10$$^{-19}$$ C.

Question 9

Which group in the periodic table contains elements that are highly reactive nonmetals?

Accepted Answer

Halogens

Question 10

A main-group metal typically forms an ion by:

Accepted Answer

Losing electrons to form a cation

Question 11

Which statement about the atomic nucleus is correct?

Accepted Answer

It contains protons and neutrons.

Question 12

What is the molar mass of helium, and how many atoms are in 8.006 g of helium?

Accepted Answer

Molar mass = 4.003 g/mol; $$\dfrac{8.006}{4.003} 	imes 6.022 	imes 10$$^{23}$$ = 1.204 	imes 10$$^{24}$$ atoms

Question 13

Which of the following is a property of nonmetals?

Accepted Answer

Poor conductor of electricity

Question 14

Which scientist is credited with proving the existence of atoms through the study of Brownian motion?

Accepted Answer

Albert Einstein

Question 15

What is the atomic number of an element, and what does it represent?

Accepted Answer

The number of protons in the nucleus

Question 16

Which of the following elements is a metalloid?

Accepted Answer

Silicon

Question 17

How many moles are present in 36.03 g of water (H$$_2O$$)? (Molar mass of H$$_2O = 18.02 g/$$mol)

Accepted Answer

$$\dfrac{36.03}{18.02} = 2.00$$ mol

Question 18

Which statement best explains why most of the mass of an atom is concentrated in the nucleus?

Accepted Answer

Protons and neutrons are located in the nucleus and are much heavier than electrons.

Question 19

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

Accepted Answer

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

Atoms and Elements: Structure, History, and Properties

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