2.3 Why elements react to form compounds?

What is the outermost electron shell called?

• Inner electron shell

• Outermost electron shell

• Core electron shell

• Central electron shell

How many electrons can the first electron shell hold?

• 2

• 8

• 18

• 1

The atomic number of an atom tells us:

• Number of neutrons

• Number of protons

• Number of electrons

• Number of shells

Atoms have no overall charge because:

• They have more electrons than protons

• They have equal numbers of protons and electrons

• They have more protons than electrons

• Neutrons balance the charge

Why don't noble gases react to form compounds?

• They have no electrons

• Their outermost shells are full

• They have no protons

• Their outermost shells are empty

What happens to sodium when it reacts to form a sodium ion?

• It gains an electron

• It loses an electron

• It becomes neutral

• It gains two protons

The symbol for a sodium ion is:

• Na−

• Na+

• Na2+

• Na3+

Chlorine becomes more stable when it:

• Loses an electron

• Gains an electron

• Loses two protons

• Gains two protons

The symbol for a chlorine ion is:

• Cl

• Cl−

• Cl+

• Cl2−

In an ionic bond, sodium and chlorine ions are held together by:

• Covalent bonding

• Electrostatic forces

• Weak interactions

• Hydrogen bonding