Question 1

Bromine is the only nonmetal that is a liquid at room temperature. Consider the isotope bromine-81,  . Select the combination which lists the correct atomic number, neutron number, and mass number, respectively.

Accepted Answer

The atomic number of bromine is 35, meaning it has 35 protons. The isotope bromine-81 has 46 neutrons (81 - 35 = 46), and the mass number is the sum of protons and neutrons, which is 81 in this case. Therefore, the correct combination is 35, 46, 81, which corresponds to choice A.

Question 2

Who is credited with discovering the atomic nucleus?

Accepted Answer

Ernest Rutherford is credited with discovering the atomic nucleus through his gold foil experiment in 1911. He found that most of the alpha particles passed straight through the foil, but a small percentage were deflected, indicating the presence of a positively charged nucleus in the center of the atom.

Question 3

Which of the following symbols does not represent an element?

Accepted Answer

HF is not a symbol for an element; it represents hydrofluoric acid, a compound made of hydrogen (H) and fluorine (F).

Question 4

The chemical symbol for potassium is

Accepted Answer

The chemical symbol for potassium is K, which comes from its Latin name "kalium".

Question 5

Which one of the following statements about atoms and subatomic particles is correct?

Accepted Answer

A neutral atom means that it has no overall charge, which means that the number of electrons (negatively charged particles) is equal to the number of protons (positively charged particles) in the atom. Therefore, option D is correct. Option A is incorrect because Rutherford discovered the nucleus by bombarding gold foil with alpha particles, not electrons. Option B is incorrect because although the masses of protons and neutrons are very similar, they are not identical. Option C is incorrect because the mass of a neutron is greater than the mass of a proton plus an electron. Option E is incorrect because the number of protons and neutrons in an atomic nucleus can vary, depending on the element.

Question 6

Atoms X, Y, Z, and R have the following nuclear compositions: Which two are isotopes?

Accepted Answer

The answer of Atoms X, Y, Z, and R have...

Question 7

An isotope of which of the following elements is chosen as a standard in measuring atomic mass?

Accepted Answer

Carbon-12 is chosen as the standard for measuring atomic mass because it is abundant, stable, and has a known number of protons, neutrons, and electrons.

Question 8

In a Millikan oil-drop experiment, the charges on several different oil drops were as follows: -5.92; -4.44; -2.96; -8.88. The units are arbitrary. What is the likely value of the electronic charge in these arbitrary units?

Accepted Answer

To find the electronic charge, we need to look for the common factor among the charges of the oil drops. We can divide all of the charges by the smallest one (which is -2.96) to get:

-5.92/-2.96 = 2
-4.44/-2.96 = 1.5
-2.96/-2.96 = 1
-8.88/-2.96 = 3

We can see that these values are all close to integers, which suggests that the actual charges are multiples of some common factor. Additionally, we can see that the smallest value that works for all of them is 0.5. For example:

-5.92/0.5 = -11.84
-4.44/0.5 = -8.88
-2.96/0.5 = -5.92
-8.88/0.5 = -17.76

Now we have charges that are all integers (albeit negative), and we can see that the common factor is likely to be the electronic charge. Therefore, in these arbitrary units, the electronic charge is approximately -0.5 x 10 = -5.

Thus, the best choice is B (-1.48) as it is closest to -5.

Question 9

What are the approximate carbon:hydrogen mass ratios in methane (CH₄) and ethyne (C₂H₂)?

Accepted Answer

The answer of What are the approximate carbon:hydrogen mass ratios...

Question 10

Millikan's oil-drop experiment

Accepted Answer

Millikan's oil-drop experiment was designed to measure the charge of an electron. Through his experiments, Millikan determined that the amount of charge carried by an electron was always a multiple of a single, fundamental charge. This established the charge on an electron with great accuracy.

Question 11

Bromine has two naturally-occurring isotopes. ⁷⁹Br has a mass of 78.9 amu and accounts for 50.3% of bromine atoms. If the atomic mass of bromine is 79.9 amu, what is the mass of an atom of the second bromine isotope?

Accepted Answer

Let x be the mass of the second bromine isotope.

We know that the average atomic mass of bromine is:

avg. mass = (mass of isotope 1)(abundance of isotope 1) + (mass of isotope 2)(abundance of isotope 2)

Substituting in the given values:

79.9 amu = (78.9 amu)(0.503) + (x)(1-0.503)

Simplifying and solving for x:

x = (79.9 - 39.8)/0.497 = 80.9 amu

Therefore, the mass of the second bromine isotope is 80.9 amu, which is answer choice D.

Question 12

One amu is defined as

Accepted Answer

One amu is defined as 1/12th the mass of an atom of carbon-12.

Question 13

Who is credited with first measuring the charge of the electron?

Accepted Answer

Robert Millikan is credited with first measuring the charge of the electron using his oil drop experiment in the early 1900s.

Question 14

Silicon, which makes up about 25% of Earth's crust by mass, is used widely in the modern electronics industry. It has three naturally occurring isotopes, ²⁸Si, ²⁹Si, and ³⁰Si. Calculate the atomic mass of silicon.

Accepted Answer

The answer of Silicon, which makes up about 25% of...

Question 15

Rutherford bombarded gold foil with alpha (α) particles and found that a small percentage of the particles were deflected. Which of the following was not accounted for by the model he proposed for the structure of atoms?

Accepted Answer

Rutherford's model accounted for the small size and charge of the nucleus, as well as the existence of protons. It also indirectly supported the presence of electrons outside the nucleus. However, the total mass of the atom was not explicitly accounted for in his model.

Question 16

Who is credited with measuring the mass/charge ratio of the electron?

Accepted Answer

J.J. Thomson is credited with measuring the mass/charge ratio of the electron using his cathode ray tube experiments. Millikan is credited with determining the charge of the electron using his oil drop experiment. Dalton and Gay-Lussac are known for their work in the development of atomic theory, while Rutherford is known for his gold foil experiment which led to the discovery of the nucleus.

Question 17

Lithium forms compounds which are used in dry cells and storage batteries and in high-temperature lubricants. It has two naturally occurring isotopes, ⁶Li (isotopic mass = 6.015121 amu) and ⁷Li (isotopic mass = 7.016003 amu). Lithium has an atomic mass of 6.9409 amu. What is the percent abundance of lithium-6?

Accepted Answer

The answer of Lithium forms compounds which are used in...

Question 18

When an atom is represented by the symbol  , the value of A is the

Accepted Answer

The answer of When an atom is represented by the...

Question 19

J. J. Thomson studied cathode ray particles (electrons) and was able to measure the mass/charge ratio. His results showed that

Accepted Answer

Thomson's discovery of cathode rays showed the existence of particles smaller than atoms, indicating that matter included particles much smaller than the atom. This was a groundbreaking discovery and laid the foundation for the development of atomic theory. He did not find evidence for a varied mass/charge ratio with different cathode materials, nor did he find evidence for dense areas of positive charge within atoms. While the concept of the minimum charge was later developed by Robert Millikan's oil drop experiment, it was not directly related to Thomson's work on cathode rays. The idea of atoms being largely empty space was later developed by Ernest Rutherford's gold foil experiment.

Question 20

Kaolinite, a clay mineral with the formula Al₄Si₄O₁₀(OH)₈, is used as a filler in slick-paper for magazines and as a raw material for ceramics. Analysis shows that 14.35 g of kaolinite contains 8.009 g of oxygen. Calculate the mass percent of oxygen in kaolinite.

Accepted Answer

The answer of Kaolinite, a clay mineral with the formula...

Quiz 2: The Components of Matter

Bromine is the only nonmetal that is a liquid at room temperature. Consider the isotope bromine-81, . Select the combination which lists the correct atomic number, neutron number, and mass number, respectively.

Who is credited with discovering the atomic nucleus?

Which of the following symbols does not represent an element?

The chemical symbol for potassium is

Which one of the following statements about atoms and subatomic particles is correct?

Atoms X, Y, Z, and R have the following nuclear compositions: Which two are isotopes?

An isotope of which of the following elements is chosen as a standard in measuring atomic mass?

In a Millikan oil-drop experiment, the charges on several different oil drops were as follows: -5.92; -4.44; -2.96; -8.88. The units are arbitrary. What is the likely value of the electronic charge in these arbitrary units?

What are the approximate carbon:hydrogen mass ratios in methane (CH₄) and ethyne (C₂H₂) ?

Millikan's oil-drop experiment

Bromine has two naturally-occurring isotopes. ⁷⁹Br has a mass of 78.9 amu and accounts for 50.3% of bromine atoms. If the atomic mass of bromine is 79.9 amu, what is the mass of an atom of the second bromine isotope?

One amu is defined as

Who is credited with first measuring the charge of the electron?

Silicon, which makes up about 25% of Earth's crust by mass, is used widely in the modern electronics industry. It has three naturally occurring isotopes, ²⁸Si, ²⁹Si, and ³⁰Si. Calculate the atomic mass of silicon.

Rutherford bombarded gold foil with alpha (α) particles and found that a small percentage of the particles were deflected. Which of the following was not accounted for by the model he proposed for the structure of atoms?

Who is credited with measuring the mass/charge ratio of the electron?

When an atom is represented by the symbol , the value of A is the

J. J. Thomson studied cathode ray particles (electrons) and was able to measure the mass/charge ratio. His results showed that

Kaolinite, a clay mineral with the formula Al₄Si₄O₁₀(OH) ₈, is used as a filler in slick-paper for magazines and as a raw material for ceramics. Analysis shows that 14.35 g of kaolinite contains 8.009 g of oxygen. Calculate the mass percent of oxygen in kaolinite.

Quiz 2: The Components of Matter

Bromine is the only nonmetal that is a liquid at room temperature. Consider the isotope bromine-81, . Select the combination which lists the correct atomic number, neutron number, and mass number, respectively.

Who is credited with discovering the atomic nucleus?

Which of the following symbols does not represent an element?

The chemical symbol for potassium is

Which one of the following statements about atoms and subatomic particles is correct?

Atoms X, Y, Z, and R have the following nuclear compositions: Which two are isotopes?

An isotope of which of the following elements is chosen as a standard in measuring atomic mass?

In a Millikan oil-drop experiment, the charges on several different oil drops were as follows: -5.92; -4.44; -2.96; -8.88. The units are arbitrary. What is the likely value of the electronic charge in these arbitrary units?

What are the approximate carbon:hydrogen mass ratios in methane (CH4) and ethyne (C2H2) ?

Millikan's oil-drop experiment

Bromine has two naturally-occurring isotopes. 79Br has a mass of 78.9 amu and accounts for 50.3% of bromine atoms. If the atomic mass of bromine is 79.9 amu, what is the mass of an atom of the second bromine isotope?

One amu is defined as

Who is credited with first measuring the charge of the electron?

Silicon, which makes up about 25% of Earth's crust by mass, is used widely in the modern electronics industry. It has three naturally occurring isotopes, 28Si, 29Si, and 30Si. Calculate the atomic mass of silicon.

Rutherford bombarded gold foil with alpha (α) particles and found that a small percentage of the particles were deflected. Which of the following was not accounted for by the model he proposed for the structure of atoms?

Who is credited with measuring the mass/charge ratio of the electron?

When an atom is represented by the symbol , the value of A is the

J. J. Thomson studied cathode ray particles (electrons) and was able to measure the mass/charge ratio. His results showed that

Kaolinite, a clay mineral with the formula Al4Si4O10(OH) 8, is used as a filler in slick-paper for magazines and as a raw material for ceramics. Analysis shows that 14.35 g of kaolinite contains 8.009 g of oxygen. Calculate the mass percent of oxygen in kaolinite.

What are the approximate carbon:hydrogen mass ratios in methane (CH₄) and ethyne (C₂H₂) ?

Bromine has two naturally-occurring isotopes. ⁷⁹Br has a mass of 78.9 amu and accounts for 50.3% of bromine atoms. If the atomic mass of bromine is 79.9 amu, what is the mass of an atom of the second bromine isotope?

Silicon, which makes up about 25% of Earth's crust by mass, is used widely in the modern electronics industry. It has three naturally occurring isotopes, ²⁸Si, ²⁹Si, and ³⁰Si. Calculate the atomic mass of silicon.

Kaolinite, a clay mineral with the formula Al₄Si₄O₁₀(OH) ₈, is used as a filler in slick-paper for magazines and as a raw material for ceramics. Analysis shows that 14.35 g of kaolinite contains 8.009 g of oxygen. Calculate the mass percent of oxygen in kaolinite.