12.5

13

25

37

9

10

19

28

ion

isotope

new element

isomer

92

147

239

331

Protons, neutrons, and electrons all have about the same mass.

Unlike protons or neutrons, electrons have no mass.

Neutrons have no charge and no mass.

An electron has far less mass than either a proton or neutron.

the number of neutrons

the charge on the electrons

the number of protons

the mass of a neutron

They do not have the same number of protons.

Their atoms have an identical mass.

They are isotopes of oxygen.

The have the same mass number.

the sum of the protons and neutrons in the atom.

twice the number of protons in one atom of the element.

a ratio based on the mass of a carbon-12 atom.

a weighted average of the masses of the element’s isotopes.

electron cloud

core

nucleus

centrino

10

18

28

8