Section 6 - Group 2

Question 1

How many electrons do group 2 elements lose when they react?

Answer 1

2

Question 2

Does reactivity increase or decrease as you go down Group 2?

Answer 2

Increase

Question 3

What are the three factors that affect how strongly an electron is held by the nucleus?

Answer 3

• Positive nuclear charge: how positive the nucleus is. A greater nuclear charge provides a stronger force of attraction between the nucleus and electrons, and makes it more difficult for the atom to donate its outer electrons.
• The second factor is that in larger atoms, the outer electrons are further away from the nucleus. The electrostatic attraction decreases in strength with distance from the source.
• Electron shielding: as the atoms in group 2 get larger, the number of full electron shells round the nucleus increases. These negative charges shield the two outer electrons from the attraction of the positive nucleus.

Question 4

Even though as you go down group 2 the nuclear charge increases as more protons are added to the nucleus, why does reactivity still increase?

Answer 4

The increase in the distance between the outer electrons and the nucleus, and the increased shielding as you go down the Group, far outweigh the increase in nuclear charge.

Question 5

As you go down group 2, does the melting point increase or decrease?

Answer 5

Decrease

Question 6

Why does melting point decrease as you go down group 2?

Answer 6

• Group 2 metals, like all other metals, are held together in a lattice structure by metallic bonds.
• The strength of the metallic bonds depend on how strong the attraction is between the positive ions and the free electrons. The more shielded the positive nuclei are, the weaker the attraction will be, and so the less energy will be required to break the bond and melt the nuclei.