Ontario Grade 9 Science Class Practice Exam

What is meant by atomic mass?

1. The number of protons in an atom.

2. The average distance between the sun and an orbiting object.

3. The mass of an atom in atomic mass units.

4. A device used to measure current.

The correct answer is: The mass of an atom in atomic mass units.

Atomic mass refers to the average mass of an atom in atomic mass units, which are defined based on the mass of a single proton or neutron. Option A is incorrect because the number of protons in an atom is referred to as its atomic number, not its atomic mass. Option B is incorrect because distance is not typically used to measure atomic mass. Option D is incorrect because a device used to measure current is typically referred to as an ammeter, not an atomic mass.