The dense, positively charged mass located in the center of the atom.

• nucleus
• proton
• isotope
• molecule

Atoms of the same element must always have the same number of _________

• electrons
• neutrons
• isotopes
• protons

The __________ of an atom is the sum of the protons and neutrons in the nucleus of that atom.

• mass number
• atomic number 
• atomic weuight
• isotope weight

Two atoms of the same element but with different mass numbers are called________

• electrons
• isotopes
• variables
• electron cloud

How many protons are in this element?

• 79
• 196
• 117
• Cannot be determined

Tags

NGSS.MS-PS1-1

How many protons are in an atom with an atomic number of 20, an atomic mass of 45, and a charge of +2?

• 20
• 10
• 2
• 18

Tags

NGSS.MS-PS1-1

Isotopes are elements with a different amount of

• protons
• neutrons
• electrons
• atoms

How many neutrons are in an atom with an atomic number of 20, an atomic mass of 45, and a charge of +2?

• 20
• 25
• 2
• 18

Tags

NGSS.MS-PS1-1

How many electrons are in an atom with an atomic number of 20, an atomic mass of 45, and a charge of +2?

• 20
• 45
• 18
• 2

Tags

NGSS.MS-PS1-1

How many electrons are in an atom that has an atomic number of 34, an atomic mass of 74 and a charge of -2?

• 34
• 36
• 2
• 40

Tags

NGSS.MS-PS1-1