4. Periodicity

Question 0

What is an element called that has some properties of a metal and some of a non-metal?

Answer 0

Metalloids or semi-metals

Question 1

Where is the step line which separates metals and non-metals?

Answer 1

From the left of Boron to the left of Astatine

Question 2

Where are semi-metals in the periodic table?

Answer 2

Elements that touch the step line

Question 3

Give an example of a semi-metal and the properties it exhibits

Answer 3

Silicon

Conducts electricity (not as well as a metal)
Shiny

Question 4

Where is the s-block on the periodic table?

Answer 4

Groups 1 and 2 (and hydrogen and helium)

Question 5

Where is the p-block on the periodic table?

Answer 5

The right hand side: groups 3,4,5,6,7 and 0 (not helium)

Question 6

Where is the d-block on the periodic table?

Answer 6

The transition metals block

Question 7

Where is the f-block on the periodic table?

Answer 7

At the very bottom underneath the d-block

Question 8

Which two d-block elements are not transition metals?

Answer 8

Zinc and scandium: they do not form compounds which have partly filled d-orbitals- a characteristic of transition metals.

Question 9

Generally how does reactivity increase in the s-block?

Answer 9

More reactive as we go down the group

Question 10

Generally how does reactivity increase in the p-block?

Answer 10

More reactive going up the group

Question 11

How reactive are the transition metals?

Answer 11

They are rather unreactive

Question 12

How do elements in group 5,6 and 7 bond?

Answer 12

They either accept electrons to form ionic compounds or share their outer electrons to form covalent compounds.

Question 13

What kind of melting points do giant structures tend to have?

Answer 13

High melting and boiling points

Question 14

What kind of melting points do molecular structures tend to have?

Answer 14

Low melting and boiling points

Question 15

Describe the trends in boiling and melting points across period 3

Answer 15

From sodium to aluminium the melting and boiling points increase (increasing number of delocalised electrons)

The melting points of the non metals in period 3 depend on the sizes of their van der Waals forces which depends on how many electrons are in their molecules.

They are therefore ordered: S8 > P4 > Cl2

Silicon with its giant structure has a much higher melting point

Question 16

What are the trends in atomic radii?

Answer 16

Atoms get larger as we go down a group

Atoms get smaller as we go across a period

Question 17

Why does the attic radii get smaller across a period?

Answer 17

The nuclear charge increases across a group but the shielding stays the same.

Question 18

Why does the radii of atoms increase down a group?

Answer 18

Going down a group there is an extra complete main level compared with the one before.

Question 19

The ionisation energy …. Across a period

Answer 19

The ionisation energy increases across a period.

Question 20

Why does he ionisation energy increase across a period?

Answer 20

The number of protons in the nucleus increases but the shielding remains the same.

Question 21

The first ionisation energy….. Down a group

Answer 21

The first ionisation energy decreases down the group

Question 22

Why does the first ionisation energy decrease as we go down the group?

Answer 22

The outer electron is further away from the nucleus and there is an increase in shielding.

Question 23

What is the trend in ionisation energy from one period to the next? (From period 0 to period 1)

Answer 23

There is a decrease in ionisation energy because there is increased shielding and he outermost electron is further from the nucleus. Hence, the electron is easier to remove.

Question 24

What are the exceptions to the increasing ionisation energies across period 3?

Answer 24

Magnesium to aluminium (decreases due to moving up from 3s to 3p)
Phosphorus to sulfur (decreases due to the electron repulsion in one of the 3p orbitals)

Question 25

What is the trend in successive ionisation energies?

Answer 25

The ionisation energy increases because it gets harder to remove the next electron. They increase more significantly when you remove an electron from the next main energy level down.