Question 1

How many electrons surround the nucleus of a neutral atom of the isotope ¹⁸O of oxygen? Oxygen has an atomic number of 8. A) 18 B) 7 C) 10 D) 8

Accepted Answer

In a neutral atom, the number of electrons equals the atomic number. For oxygen, with an atomic number of 8, there are 8 electrons surrounding the nucleus.

Question 2

Of the four combinations of particles that form the nuclei of atoms, which one does NOT make up the nucleus of an isotope of the same element as the other three?
A) 7 protons, 9 neutrons
B) 8 protons, 10 neutrons
C) 8 protons, 9 neutrons
D) 8 protons, 8 neutrons

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons. Choices B, C, and D all have 8 protons, making them isotopes of the same element. Choice A has 7 protons, making it a different element.

Question 3

How do the nuclei of the isotopes ¹⁴C of carbon and ¹⁴N of nitrogen differ from each other? A) The nuclei have the same number of protons but a different number of neutrons. B) The nuclei are identical; the isotopes differ only in the number of electrons. C) The nuclei have different numbers of both protons and neutrons. D) The nuclei have the same number of neutrons but a different number of protons.

Accepted Answer

The nucleus of ¹⁴C has 6 protons and 8 neutrons, while the nucleus of ¹⁴N has 7 protons and 7 neutrons.

Question 4

Which of these properties of the isotopes ¹⁵N (nitrogen) and ¹⁵O (oxygen) are very nearly the same? A) number of protons in the nucleus B) number of neutrons in the nucleus C) nuclear mass and number of neutrons in the nucleus D) nuclear mass

Accepted Answer

Both isotopes have a similar nuclear mass because they have the same mass number (15), despite having different numbers of protons and neutrons.

Question 5

The isotope ²⁰Ne has an atomic number of 10. The nucleus of this isotope contains _____ protons and _____ neutrons. A) 9; 11 B) 20; 20 C) 11; 9 D) 10; 10

Accepted Answer

The atomic number, which is 10 for this isotope, indicates the number of protons, which is 10. The mass number (²⁰Ne) suggests a total of 20 nucleons (protons + neutrons). With 10 protons, there must be 10 neutrons to make the total 20.

Question 6

The carbon isotope ¹⁴C is not useful for most radioactive dating in astronomy because A) it is not radioactive. B) it is too rare. C) its half-life is too short. D) its half-life is too long.

Accepted Answer

Carbon-14 has a half-life of about 5,730 years, which is too short for dating astronomical objects that are millions or billions of years old.

Question 7

Element A decays into element B with a half-life of 700 million years. An astronomer finds a rock that she knows was formed originally without any B present. But the rock now contains both A and B, with the A+B portion of the rock being 1/8 A and 7/8 B. How old is the rock?
A) 350 million years
B) 700 million years
C) 1.4 billion years
D) 2.1 billion years

Accepted Answer

The rock is 2.1 billion years old. Initially, the rock was all A with no B. After each 700 million years (the half-life of A), the amount of A halves. The ratio of A to B is 1/8 to 7/8, indicating that three half-lives have passed (since $1/2^3 = 1/8$), totaling 2.1 billion years (700 million years x 3).

Question 8

If one neutron is added to a nucleus of an isotope of carbon, ¹²C, in a particular nuclear reaction, the result will be A) (¹¹C.) B) (¹³C.) C) (¹²O.) D) (¹³O.)

Accepted Answer

Adding a neutron to a nucleus changes its mass number (the sum of protons and neutrons) but not its atomic number (the number of protons, which determines the element). Therefore, the isotope of carbon will remain carbon but with an increased mass number by one.

Question 9

Suppose that at some time a particular sample of radioactive material contains N radioactive atoms (e.g., N might be 1 billion radioactive atoms). How many radioactive atoms will be left after 3 half-lives have passed?
A) 1/6 N
B) 1/8 N
C) 0
D) 1/2 N

Accepted Answer

After each half-life, the number of radioactive atoms is reduced by half. Therefore, after 3 half-lives, the amount of radioactive material left would be N/2 (after the first half-life) then (N/2)/2 = N/4 (after the second half-life), and finally (N/4)/2 = N/8 (after the third half-life).

Question 10

Iron has 26 protons, and one isotope of iron, ⁵⁷Fe, has an atomic mass of about 57. How many neutrons are in the nucleus of this atom? A) 31 B) 83 C) 26 D) 57

Accepted Answer

The number of neutrons in an atom can be found by subtracting the number of protons from the atomic mass number. For iron (Fe) with an atomic mass of about 57 and 26 protons, the calculation is 57 - 26 = 31 neutrons.

Question 11

One isotope of iron has an atomic number of 26. How many protons are there in its nucleus?
A) The atomic number is not related to the number of protons in the nucleus, which could be any number between 1 and 26.
B) 1 less than 26, or 25
C) 26
D) 56

Accepted Answer

The atomic number of an element is equal to the number of protons in its nucleus. Since the atomic number of iron is given as 26, it means there are 26 protons in its nucleus.

Question 12

Carbon-14 (¹⁴C) has a half-life of approximately 6000 years. A researcher investigating a piece of ancient wood determines that there is only 1/4 as much ¹⁴C present in the wood now as there was when the tree that the wood came from was alive. How old is the piece of wood? A) 12,000 years B) The age cannot be determined from this information. C) 9000 years D) 24,000 years

Accepted Answer

The piece of wood is 12,000 years old because the amount of Carbon-14 has halved twice (from 100% to 50% to 25%), and with each halving taking approximately 6000 years, two halvings equal 12,000 years.

Question 13

Considering the oxygen isotopes ¹⁵O and ¹⁶O, which of these properties is/are very nearly the same for both isotopes? A) number of protons in the nucleus B) mass of the nucleus C) nuclear mass and number of neutrons in the nucleus D) number of neutrons in the nucleus

Accepted Answer

The number of protons in the nucleus determines the element, and since both isotopes are of oxygen, they have the same number of protons. The difference in isotopes comes from the number of neutrons, not protons.

Question 14

How many electrons surround the nucleus of a neutral atom of iron, which has an atomic number of 26?
A) 26
B) 27
C) 52
D) 25

Accepted Answer

In a neutral atom, the number of electrons equals the atomic number, which for iron (Fe) is 26.

Question 15

When an atom of the radioactive carbon isotope ¹⁴C decays into ¹⁴N (nitrogen), what happens in the nucleus of the atom? A) The nucleus of the carbon atom captures a nucleus of a hydrogen atom (a proton). B) A proton is ejected from the nucleus. C) A neutron becomes a proton. D) A neutron is ejected from the nucleus.

Accepted Answer

When a carbon atom decays into a nitrogen atom, a neutron in the nucleus of the carbon atom changes into a proton. This process increases the atomic number by one, converting the element from carbon to nitrogen.

Question 16

The atomic number of the isotope ²³⁸U of uranium is 92. The nucleus of this isotope contains A) 92 protons and 146 neutrons. B) 92 protons, 54 neutrons, and 92 electrons. C) 184 protons, 92 electrons, and 54 neutrons. D) 146 protons and 92 neutrons.

Accepted Answer

The atomic number, which is 92 for uranium, indicates the number of protons in the nucleus. The mass number (238 in this case) minus the atomic number gives the number of neutrons (238 - 92 = 146). Therefore, the nucleus contains 92 protons and 146 neutrons.

Question 17

What is the half-life of a sample of matter containing a radioactive element?
A) time needed for the radioactive atoms to build up half the energy needed to decay
B) half the time needed for the radioactive decay rate to double
C) time needed for half the radioactive atoms in the sample to decay
D) half the time needed for all the radioactive atoms in the sample to decay

Accepted Answer

The half-life of a radioactive element is defined as the time required for half of the radioactive atoms in a sample to undergo decay. This is a fundamental concept in nuclear physics and radiometric dating.

Question 18

What is the total number of protons and neutrons in the nucleus of an atom of the fissionable isotope of uranium used in nuclear weapons, ²³⁵U, which has an atomic number of 92? A) 235 B) 92 C) 143 D) 327

Accepted Answer

The total number of protons and neutrons in the nucleus of an atom is given by its mass number, which for the fissionable isotope of uranium used in nuclear weapons (U-235) is 235.

Question 19

Suppose that a particular sample of wood contains 10²⁰ atoms of the radioactive isotope ¹⁴C. The half-life of ¹⁴C is about 6000 years. Approximately how long will it take for all the ¹⁴C atoms to decay to ¹⁴N? A) infinite amount of time B) 12,000 years C) 3000 years D) 6000 years

Accepted Answer

Radioactive decay is a process that does not have a definite end as it is asymptotic, meaning the quantity of the radioactive isotope approaches zero but never actually reaches it. Therefore, it would take an infinite amount of time for all atoms of a radioactive isotope to decay.

Question 20

The isotope ¹⁵N has an atomic number of 7. The nucleus of this isotope contains A) 7 protons and 8 neutrons. B) 7 neutrons and 15 protons. C) 7 protons and 15 neutrons. D) 7 neutrons and 8 protons.

Accepted Answer

The atomic number (7) indicates the number of protons, and the mass number (15) is the sum of protons and neutrons. Therefore, it has 7 protons and 8 neutrons.

Quiz 4: Atomic Physics and Spectra

How many electrons surround the nucleus of a neutral atom of the isotope ¹⁸O of oxygen? Oxygen has an atomic number of 8.

Of the four combinations of particles that form the nuclei of atoms, which one does NOT make up the nucleus of an isotope of the same element as the other three?

How do the nuclei of the isotopes ¹⁴C of carbon and ¹⁴N of nitrogen differ from each other?

Which of these properties of the isotopes ¹⁵N (nitrogen) and ¹⁵O (oxygen) are very nearly the same?

The isotope ²⁰Ne has an atomic number of 10. The nucleus of this isotope contains _ protons and _ neutrons.

The carbon isotope ¹⁴C is not useful for most radioactive dating in astronomy because

Element A decays into element B with a half-life of 700 million years. An astronomer finds a rock that she knows was formed originally without any B present. But the rock now contains both A and B, with the A+B portion of the rock being 1/8 A and 7/8 B. How old is the rock?

If one neutron is added to a nucleus of an isotope of carbon, ¹²C, in a particular nuclear reaction, the result will be

Suppose that at some time a particular sample of radioactive material contains N radioactive atoms (e.g., N might be 1 billion radioactive atoms) . How many radioactive atoms will be left after 3 half-lives have passed?

Iron has 26 protons, and one isotope of iron, ⁵⁷Fe, has an atomic mass of about 57. How many neutrons are in the nucleus of this atom?

One isotope of iron has an atomic number of 26. How many protons are there in its nucleus?

Carbon-14 (¹⁴C) has a half-life of approximately 6000 years. A researcher investigating a piece of ancient wood determines that there is only 1/4 as much ¹⁴C present in the wood now as there was when the tree that the wood came from was alive. How old is the piece of wood?

Considering the oxygen isotopes ¹⁵O and ¹⁶O, which of these properties is/are very nearly the same for both isotopes?

How many electrons surround the nucleus of a neutral atom of iron, which has an atomic number of 26?

When an atom of the radioactive carbon isotope ¹⁴C decays into ¹⁴N (nitrogen) , what happens in the nucleus of the atom?

The atomic number of the isotope ²³⁸U of uranium is 92. The nucleus of this isotope contains

What is the half-life of a sample of matter containing a radioactive element?

What is the total number of protons and neutrons in the nucleus of an atom of the fissionable isotope of uranium used in nuclear weapons, ²³⁵U, which has an atomic number of 92?

Suppose that a particular sample of wood contains 10²⁰ atoms of the radioactive isotope ¹⁴C. The half-life of ¹⁴C is about 6000 years. Approximately how long will it take for all the ¹⁴C atoms to decay to ¹⁴N?

The isotope ¹⁵N has an atomic number of 7. The nucleus of this isotope contains

Quiz 4: Atomic Physics and Spectra

How many electrons surround the nucleus of a neutral atom of the isotope 18O of oxygen? Oxygen has an atomic number of 8.

Of the four combinations of particles that form the nuclei of atoms, which one does NOT make up the nucleus of an isotope of the same element as the other three?

How do the nuclei of the isotopes 14C of carbon and 14N of nitrogen differ from each other?

Which of these properties of the isotopes 15N (nitrogen) and 15O (oxygen) are very nearly the same?

The isotope 20Ne has an atomic number of 10. The nucleus of this isotope contains _____ protons and _____ neutrons.

The carbon isotope 14C is not useful for most radioactive dating in astronomy because

Element A decays into element B with a half-life of 700 million years. An astronomer finds a rock that she knows was formed originally without any B present. But the rock now contains both A and B, with the A+B portion of the rock being 1/8 A and 7/8 B. How old is the rock?

If one neutron is added to a nucleus of an isotope of carbon, 12C, in a particular nuclear reaction, the result will be

Suppose that at some time a particular sample of radioactive material contains N radioactive atoms (e.g., N might be 1 billion radioactive atoms) . How many radioactive atoms will be left after 3 half-lives have passed?

Iron has 26 protons, and one isotope of iron, 57Fe, has an atomic mass of about 57. How many neutrons are in the nucleus of this atom?