AP Chemistry : Isotopes

Study concepts, example questions & explanations for AP Chemistry

varsity tutors app store varsity tutors android store

Example Questions

← Previous 1

Example Question #1 : Elements And Atoms

Which of the following is an isotope of Fluorine-20

Possible Answers:
Fluorine 2-
Neon - 20
Iron
Fluorine - 18
Oxygen
Correct answer: Fluorine - 18
Explanation:

isotopes have more neutrons, but their protons are the same

Example Question #1 : Isotopes

Which of the following contains the most neutrons?

Possible Answers:

Oxygen-15

Carbon-12

Nitrogen-14

Carbon-14

Boron-12

Correct answer:

Carbon-14

Explanation:

The number following the compound is the isotope number, giving the number of protons and neutrons the element contains per atom. To get the number of neutrons you take the isotope number and subtract the atomic number of that element. 

Example Question #2 : Isotopes

Which of the following is NOT an isotope of oxygen

Possible Answers:

O2

14O

O2-

oxygen- 16

oxygen-14

Correct answer:

O2-

Explanation:

O2- is an ion, and not an isotope; an isotope has the same number of protons and electrons, but a different number of neutrons

Example Question #2 : Elements, Ions, And Isotopes

Which of the following isotopes has the greatest number of neutrons?

Possible Answers:

Fluorine-16

Oxygen-15

Nitrogen-13

Boron-10

Carbon-14

Correct answer:

Carbon-14

Explanation:

Carbon-14 has 8 neutrons

Nitrogen-13 has 6 neutrons

Oxygen-15 has 7 neutrons

Fluorine-16 has 7 neutrons

Boron-10 has 5 neutrons

Example Question #1 : Isotopes

What is the correct notation of the isotope of nitrogen with 8 neutrons?

Possible Answers:

Nitrogen-14

Nitrogen-15

Nitrogen-7

None of these

Nitrogen-8

Correct answer:

Nitrogen-15

Explanation:

The denotation is element name-proton+neutron. With 7 protons and 8 neutrons, this necomes Nitrogen-15.

Example Question #1 : Elements And Atoms

A Carbon-12 atom that has gained a neutron and lost an electron can be described as:

Possible Answers:

an isotope, and a positive ion.

a positive ion only

an isotope, and a negative ion.

an isotope only

a negative ion only

Correct answer:

an isotope, and a positive ion.

Explanation:

Isotopes are examples of the same element existing with different amounts of nuetrons.  When an atom gains a neutron, a different isotope of this atom has been formed.  Ions are atoms that have either completely lost or completely gained an electron when compared to their ground state configuration.  Here the atom has lost an electron and is thus a positive ion. 

Example Question #1 : Elements, Ions, And Isotopes

Which of the following is a set of isotopes?

Possible Answers:

 and 

 and 

 and 

 and 

 and 

Correct answer:

 and 

Explanation:

Isotopes are members of the same element that have a different number of neutrons, and therefore a different atomic weight. The number shown in the top left is always the number of protons plus neutrons (atomic weight), so we can show that an element is an isotope by increasing or decreasing that number.

There are three main isotopes of carbon: carbon-12, carbon-13, and carbon-14. The identity of the element must not change, only the atomic weight. The other answer choices are other types of related chemicals; note that ions are not isomers.

Example Question #1 : Isotopes

An element has two main isotopes. The first isotope has a molar mass of 125 grams, and the second isotope has a molar mass of 128 grams. A naturally occurring sample of the element has a molar mass of 126.8 grams.

Which of the following statements is true concerning the heavier isotope?

Possible Answers:

It has less neutrons than the lighter isotope

Both isotopes have the same number of nucleons

It has more protons than the lighter isotope

It has more neutrons than the lighter isotope

Correct answer:

It has more neutrons than the lighter isotope

Explanation:

When comparing isotopes to one another, remember that they differ by the number of neutrons in the nucleus. A heavier isotope will have more neutrons when compared to a lighter isotope. The number of protons cannot change, as this would change the elemental identity of the compound. The only way to change the atomic mass of an isotope is to change the number of neutrons.

Example Question #51 : Ap Chemistry

The well-known uranium-235 isotope has how many protons, neutrons, and electrons?

Possible Answers:

143 protons, 92 neutrons, and 143 electrons

92 protons, 143 neutrons, and 143 electrons

92 protons, 235 neutrons, and 92 electrons

92 protons, 143 neutrons, and 92 electrons

235 protons, 92 neutrons, and 235 electrons

Correct answer:

92 protons, 143 neutrons, and 92 electrons

Explanation:

We can start by identifying the atomic number of uranium, which will also be equal to the number of protons. For uranium, the atomic number is 92.

The isotope mass is given in the name of the isotope, in this case uranium-235. The total mass (sum of the protons and neutrons) will be equal to 235.

To find the number of neutrons, subtract the number of protons from the total mass: .

Finally, for any neutrally charged molecule, the number of electrons will be equal to the number of protons (92).

Our final answer is 92 protons, 143 neutrons, and 92 electrons.

Example Question #52 : Ap Chemistry

Which isotope of nitrogen has the largest atomic radius?

Possible Answers:

The isotopes have the same atomic radius

Correct answer:

The isotopes have the same atomic radius

Explanation:

Atomic radius is generally affected by the interactions of protons and electrons in the atom. Protons attract electrons, condensing the atom, but electrons repel each other, expanding the atom.

Isotopes represent variations in the number of neutrons found in a atom. Neutrons have no charge and neither attract nor repel the electron cloud. As such, increasing the number of neutrons should have no effect on the atomic radius. Each nitrogen isotope has the same atomic radius.

← Previous 1
Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: