CHAPTER 7: Periodicity

Question 1

Define PERIODICITY.

Answer 1

The repeating trend in properties of elements across each PERIOD.

Question 2

What do elements in the same GROUP share?

Answer 2

Same number of electrons in highest outer energy level.

Question 3

BLOCKS are divided according to the sub-shell with the highest energy.
So what block is Oxygen in? And Sodium?

Answer 3

Oxygen = p-block
Sodium= s-block

Question 4

What group are the HALOGENS?

Answer 4

group 17 (7)

Question 5

What is ionisation energy a measure of?

Answer 5

a measure of how easily electrons are lost from an atom to form positive ions

Question 6

Define FIRST IONISATION ENERGY.

Answer 6

the energy required to remove ONE electron from each atom in one mole of GASEOUS atoms of an element to form one mole of gaseous 1+ ions.

Question 7

Define SECOND IONISATION ENERGY.

Answer 7

the energy required to remove ONE electron from each atom in one mole of GASEOUS atoms of an element to form one mole of gaseous 2+ ions.

Question 8

Why is second ionisation energy greater than the first ionisation energy?

Answer 8

More energy is required to remove the next electron in the highest energy level because the nuclear attraction for that electron becomes stronger.

Question 9

What are the 3 factors that affect ionisation energy?

Answer 9

• Atomic Radius: greater distance between nucleus and outer shell means less nuclear attraction.
• Electron shielding: electrons repel so more shielding leads to more repulsion so less nuclear attraction for outer electrons

Question 10

How many ionisation energies does an element have?

SUCCESSIVE IONISATION

Answer 10

The same number of electrons that they have.

Question 11

Give the first and second ionisation equation for hydrogen.

Answer 11

H(g) -> H+(g) + e- FIRST IONISATION ENERGY

H+(g) -> H2+(g) + e- SECOND IONISATION ENERGY

Question 12

What should you remember about reading a successive ionisation energy graph of an element?

Answer 12

That the first few ionisation energies are for the OUTER shell, so you are counting the electrons from the OUTSIDE IN.

Question 13

What 3 things can you predict from successive ionisation energies?

Answer 13

1) number of electrons in outer shell and therefore the GROUP
2) number of shells
3) the identity of the element

Question 14

What does a large jump in ionisation energies of successive ionisation energies indicate?

Answer 14

A new, different shell

Question 15

Why is there an increased jump when you reach a new shell?

Answer 15

The next shell is closer to the nucleus so a lot more energy is required to overcome the nuclear electrostatic attraction.

Question 16

What is the trend of first ionisation energies DOWN A GROUP? why?

Answer 16

it decreases because less energy is required to overcome nuclear attraction.

• Atomic radius increases
• more shielding

Question 17

What is the trend of first ionisation ACROSS A PERIOD?

Answer 17

a GENERAL increase.

but there are 2 falls.

Question 18

Explain the 2 falls that occur across the trend of first ionisation energies of a period.

Answer 18

the first fall = removing an electron that is starting to fill a p-subshell. (a higher energy level than the previous s-subshell)

the second fall = removing the electron that is starting to pair with the electrons in an orbital. The repulsion leads to less energy required.

(see page 98)

Question 19

Metals vary in properties but what common properties do all metals have?

Answer 19

• they all have the ability to CONDUCT ELECTRICITY.
• Strong metallic bonds
• High melting and boiling points

Question 20

What is METALLIC BONDING?

Answer 20

BONDING FOR METALS:

• in a solid metal structure, each atom has donated its outer shell electrons to a pool of electrons that are delocalised throughout the structure.
• The positive ions (cations) and delocalised electrons form an electrostatic attraction.

The cations are FIXED. Only the delocalised electrons are able to move.

Question 21

Why can metals conduct electricity?

Answer 21

The delocalised electrons act as MOBILE CHARGE CARRIERS and can carry the charge across the structure when voltage is applied.

Question 22

Why do metals have high melting and boiling points?

Answer 22

Large amount of energy is required to overcome the strong electrostatic attraction between the cations and electrons (metallic bonds)

Question 23

Are metals SOLUBLE?

Answer 23

no.

interactions with solvents are rather REACTIONS.

Question 24

What are GIANT COVALENT LATTICES?

Answer 24

When MANY atoms are held together by numerous strong covalent bonds to give a 3D structure.

Question 25

What are GIANT METALLIC LATTICES?

Answer 25

When MANY atoms are held together by metallic bonding to form a 3D lattice.

Question 26

Why do GIANT COVALENT Lattices have HIGH melting and boiling points?

Answer 26

The covalent bonds are strong so lots of energy is required.

Question 27

Are giant covalent lattices soluble?

Answer 27

No, the covalent bonds are too strong to be overcome by interaction with solvents.

Question 28

Can giant lattice conduct electricity?

Answer 28

No.

EXCEPT graphite and graphene.

Question 29

Why can Graphite and Graphene conduct electricity but diamond can’t?

Answer 29

In diamond, all electrons of carbon atom is being used in covalent bonds.
In graphite and graphene, the carbon atoms are arranged in PLANAR HEXAGONAL LAYERS with spare electrons delocalised within the layers. These act as mobile charge carries and carry charge across the lattice.

Question 30

Describe the PERIODIC trend in melting points.

Answer 30

-General increase from group 1 to group 14 (4) as metals and giant covalent lattices have high melting points.
-Sharp decrease between giant molecular structures and the simple molecules as the forces are weak.
(page 103)