PS 04.3 Isotopes and Atomic Mass

What is the primary function of a mass spectrometer?

• To measure the speed of light

• To determine the average atomic mass

• To calculate gravitational force

• To analyze sound waves

Answer explanation

The primary function of a mass spectrometer is to determine the average atomic mass of particles by measuring their mass-to-charge ratio, making 'To determine the average atomic mass' the correct choice.

What is the atomic number?

• The number of protons in an atom

• The total number of electrons and neutrons

• The number of neutrons in an atom

• The total number of protons and neutrons

Answer explanation

The atomic number is defined as the number of protons in an atom. This value determines the element's identity and its position in the periodic table, making the first answer choice the correct one.

What is the mass number?

• The number of protons in an atom

• The total number of electrons

• The total number of protons and neutrons

• The number of neutrons in an atom

Answer explanation

The mass number is defined as the total number of protons and neutrons in an atom's nucleus. It reflects the atom's overall mass, as electrons contribute negligibly to mass.

What is an isotope?

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

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

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

• Atoms with the same number of protons and electrons

Answer explanation

An isotope is defined as atoms that have the same number of protons, which determines the element, but differ in the number of neutrons. This difference in neutrons results in different atomic masses for the isotopes of an element.

What does the atomic number represent in an atom?

• The total number of protons and neutrons

• The number of protons in the nucleus

• The number of electrons in the outer shell

• The total mass of the atom

Answer explanation

The atomic number represents the number of protons in the nucleus of an atom. This defines the element and its properties, making it the correct choice among the options provided.

What is the mass number of an atom?

• The number of protons in the nucleus

• The number of electrons in the atom

• The total number of protons and neutrons

• The number of neutrons only

Answer explanation

The mass number of an atom is the total number of protons and neutrons in its nucleus. This is important because it determines the atom's overall mass and is distinct from the number of electrons or neutrons alone.

What is A-Z notation used for?

• To represent the number of electrons

• To denote the atomic mass

• To show the shorthand notation of an atom's composition

• To calculate the density of an atom

Answer explanation

A-Z notation is used to represent the shorthand notation of an atom's composition, indicating the element's symbol along with its atomic number and mass number, making it easier to understand atomic structure.

Tags

NGSS.MS-PS1-1

What are isotopes?

• Atoms with the same mass number but different atomic numbers

• Atoms with the same atomic number but different mass numbers

• Atoms with different numbers of electrons

• Atoms with identical numbers of protons and neutrons

Answer explanation

Isotopes are atoms that have the same atomic number (number of protons) but different mass numbers (number of protons plus neutrons). This means they are the same element but have different numbers of neutrons.

What is a mass spectrometer used for?

• Measuring the volume of liquids

• Determining the masses of atoms, molecules, and molecular fragments

• Calculating the speed of light

• Measuring temperature changes

Answer explanation

A mass spectrometer is specifically designed to determine the masses of atoms, molecules, and molecular fragments, making it essential for analyzing chemical compositions and structures.

What does percent abundance refer to?

• The percentage of water in a solution

• The percentage of atoms of a particular isotope in a naturally occurring sample of the pure element

• The percentage of oxygen in the air

• The percentage of carbon in organic compounds

Answer explanation

Percent abundance specifically refers to the percentage of atoms of a particular isotope found in a naturally occurring sample of that element, making the second choice the correct answer.