Topic 2

What is the smallest unit of matter? It is composed of protons and neutrons, held together in the nucleus, and electrons around the nucleus in different electron orbitals, which form an electron cloud.

• cell

• nucleus

• atom

• electron

What is a subatomic particle with a positive charge that is in the nucleus of an atom?

• neutron

• proton

• electron

• valence electron

What is a subatomic particle without an electric charge, located in the nucleus of an atom?

• neutron

• proton

• electron

• valence electron

What is the center of an atom containing protons and neutrons?

• nucleus

• neutron

• proton

• electron cloud

What is the number of protons in the nucleus of an atom that determines the chemical properties of an atom?

• mass number

• atomic mass

• atomic number

• atomic symbol

What is the combined mass of all the protons and neutrons of an atom and is approximately equal to the number of protons and neutrons?

• atomic mass

• atomic number

• subatomic particles

• nucleus weight

What is the atomic number of this atom?

• 1

• 3

• 4

• 7

Most of the mass in an atom is made up of _____________________?

• protons and electrons
• protons and neutrons
• neutrons and electrons
• electrons and quarks

How many protons does sulfur have?

• 32

• 16

• 48

• 12

In an atom, the number of protons is equal to the number of ____________.

• energy levels

• neutrons

• neurons

• electrons