8THS

__________ are negatively charged particles that are in the orbitals around the nucleus.

Which two particles have mass?

An atom’s mass number is 210 and its atomic number is 85. Based on this evidence, how many neutrons does the atom have?

• 85

• 125

• 210

• 295

Why is the mass of an atom’s electrons not included in the atom’s mass number?

• The electrons move so fast that their mass cannot be measured.

• The electrons’ negative charge cancels out their masses.

• The electrons’ mass is represented in the atomic number

• The electrons are much less massive than the rest of the atom.

What are the four main ideas of Dalton's theory of the atom?

Which of these particles is the smallest?

• An atom

• a nucleus

• a proton

• an electron

Which scientist model helped other scientist predict the chemical properties of elements? What is the year?

An __________ can lose or gain electrons. When that happens we refer to it as an _______

Compare the charges and masses of protons, neutrons, and electrons?

How does the current model of the atom differ from J.J Thomson's model?