For an atom to be neutral, the number of protons must equal the number of neutrons.

• true
• false

The sum of the number of protons and neutrons in an atom is the mass number.

• true
• false

The atomic number of an element is determined by its number of protons.

• true
• false

Every atom of the same element has the same atomic number.

• true
• false

Elements arranged in vertical columns in the periodic table are called periods.

• true
• false

Dot diagrams are used to represent

• atomic numbers
• atomic mass
• isotopes
• outer level electrons

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

A certain atom has 26 protons, 26 electrons, and 30 neutrons.  Its mass number is

• 26
• 30
• 52
• 56

Atoms of the same element with different numbers of neutrons are called

• isotopes
• metals
• metalloids
• radioactive elements

Tags

NGSS.HS-PS1-8

A particle that moves around the nucleus is a(n)

• electron
• proton
• neutron
• quark

Most of the mass of an atom is found in its

• nucleus
• electron cloud
• atomic number
• mass number