2. Trends in periodic table

Question 1

What is covalent radius?

Answer 1

Half the distance between bonding nuclei

Question 2

Why is there no covalent radii for the Noble Gases?

Answer 2

They do not form covalent bonds.

Question 3

What is the trend for covalent radius across a period?

Answer 3

Decreases due to greater pull of extra protons on shells

Question 4

What is the trend for covalent radius down a group?

Answer 4

Increases due to greater number of electron shells (levels)

Question 5

What is 1st Ionisation energy?

Answer 5

The energy required to remove 1 mole of electrons from 1 mole of atoms in the gaseous state

Question 6

What is the trend for ionisation energy across a period?

Answer 6

Increases due to greater pull of extra protons on outer electrons

Question 7

What is the trend for ionisation energy going down a group?

Answer 7

Decreases due to greater shielding effect of extra shells and greater distance of outer electrons from nucleus

Question 8

Why is 2nd ionisation energy always greater than the 1st?

Answer 8

It takes more energy to remove an electron from a positively charged ion

Question 9

Why is the 2nd ionisation energy of group 1 metals so much higher than the 1st?

or

Why is the 3rd ionisation energy of group 2 metals so much higher than the 2nd?

or

Why is the 4rd ionisation energy of group 3 metals so much higher than the 3rd?

Answer 9

• electron is being removed from a stable (full) shell or electron arrangement
• this shell has less shielding effect from the nucleus
• this shell lies closer to the nucleus

Question 10

What is electronegativity?

Answer 10

The attraction an atom’s nucleus has for bonding electrons

Question 11

What is the trend fo electronegativity down a group

Answer 11

Decreases due to greater shielding effect of extra shells and greater distance of bonding electrons from nucleus

Question 12

What is the trend for electronegativity across a period

Answer 12

Increases due to greater pull of extra protons on shared pair of electrons

Question 13

Ionic radius going down a group

Answer 13

Increases due to extra electron shells being added as you go down group

Question 14

How do the ionic radii of metals compare to corresponding covalent radii?

Answer 14

Ionic radii are smaller due to outer electrons being lost leading to 1 shell fewer

Question 15

How do the ionic radii of non-metals compare to corresponding covalent radii

Answer 15

Ionic radii are greater due to extra electrons on outer shell causing greater repulsion between shells.