Path to Mastering LT 2.2 - Isotopes

What is the definition of isotopes?

• Atoms with the same number of protons but different numbers of neutrons

• Atoms with different numbers of protons and neutrons

• Atoms with the same number of neutrons but different numbers of protons

• Atoms with the same number of protons and neutrons

Answer explanation

Which of the following is an example of isotopes?

• Carbon-12 and Carbon-14

• Oxygen-16 and Nitrogen-14

• Hydrogen-1 and Helium-4

• Sodium-23 and Magnesium-24

Answer explanation

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons, meaning that their mass number varies.

How do isotopes of the same element differ?

• They have varying number of protons but the same atomic mass.

• They have different atomic masses due to varying numbers of neutrons.

• They have different atomic masses due to varying numbers of protons.

• They have different atomic masses due to varying numbers of electrons.

Answer explanation

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons, meaning that their mass number varies.

Explain why isotopes of the same element have different atomic masses.

• Because they have different numbers of electrons

• Because they have different numbers of neutrons

• Because they have different numbers of protons

• Because they have different numbers of atoms

Answer explanation

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons, meaning that their mass number varies.

Consider the isotopes of chlorine: Chlorine-35 and Chlorine-37. What is the difference in their atomic masses?

• Chlorine-35 has a higher atomic mass than Chlorine-37.

• Chlorine-37 has a higher atomic mass than Chlorine-35.

• Both have the same atomic mass.

• Chlorine-35 has a lower atomic mass than Chlorine-37.

Answer explanation

In the case of Chlorine -35 and Chlorine -37, the numbers 35 and 37 are the respective masses of the two isotopes. Chlorine-37 has a greater atomic mass (37 amu) than Chlorine-35 (35 amu). Each isotope of Chlorine has 17 protons. The difference in mass comes from the difference in the number of neutrons in each isotope.

If an element has isotopes with atomic masses of 10 and 11, what can you infer about the number of neutrons in these isotopes?

• Both isotopes have the same number of neutrons.

• The isotope with atomic mass 11 has one more neutron than the isotope with atomic mass 10.

• The isotope with atomic mass 10 has one more neutron than the isotope with atomic mass 11.

• The number of neutrons cannot be determined from the atomic mass.

Answer explanation

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons, meaning that their mass number varies. Atomic mass = protons + neutrons, since the number of protons must be the same the difference in atomic mass is because of a difference in the number of neutrons.

Which isotope has 4 neutrons?

Answer explanation

neutrons = mass number - protons

What do these isotopes of carbon all have in common?

• neutrons & mass number
• atomic number and neutrons
• atomic number and protons

• protons, atomic number, and mass number

Answer explanation

Isotopes are atoms of the same element that have the same number of protons (i.e., atomic number, "Z") but a different number of neutrons, meaning that their mass number, "A", varies. Atomic number = the number of protons.

Tags

NGSS.HS-PS1-8