What is the maximum number of electrons that the first electron shell can hold?

• 2

• 18

• 8

• 4

How many electrons are present in the second shell of substance M?

• 2

• 10

• 8

• 3

What must be true about the number of protons and electrons in a neutral atom?

• Protons are double the electrons

• Protons are always more than electrons

• They must be equal

• Electrons are always more than protons

Which element has a proton number of 13?

• Nitrogen

• Aluminum

• Oxygen

• Carbon

What does the mass number of an element represent?

• Number of protons only

• Number of protons and neutrons

• Number of electrons

• Number of neutrons only