Unit 2 Review

How many valence electrons are in the electron configuration 1s²2s²2p⁶3s²3p⁴?

• 2

• 4

• 6

• 16

What did Rutherford discover about atoms?

• An atom is always negatively charged.

• An atom is mostly empty space, but has a dense positively charged center(nucleus).

• An atom is always positively charged.

• All particles will pass straight through gold foil with no change in path.

Cations have what charge?

• +

• -

How many valence electrons are represented here?

• 7
• 5
• 2
• 8

How many valence electrons are in the atom shown in the picture?

• 2

• 3

• 5

What atom matches this electron configuration?
1s²2s²2p⁶3s²3p⁶4s²3d¹⁰

• Zinc
• Copper
• Nickel
• Germanium

What is this element? 
[Ar]4s²

• Calcium
• Sodium
• Scandium
• Titanium

How many neutrons are in the isotope of sulfur,³⁶S?

• 16

• 20

• 24

• 26

Which of the following does NOT differ in isotopes of the same element?

• mass number

• number of neutrons

• number of protons

• chemical properties

What isotope is shown here? (Red = protons, gray = neutrons, blue = electrons)

• Beryllium-5

• Beryllium-9

• Boron-4

• Boron-9