Chapter 7: Periodicity

Question 1

How did Mendeleev arrange his periodic table?

Answer 1

Mendeleev arranged his table by
- increasing atomic mass
- chemical properties

Question 2

How is the modern periodic table arranged?

Answer 2

• increasing atomic number
• repeating trends in physical and chemical properties (periodicity)
• similar chemical properties

Question 3

Trend in electron configurations

Answer 3

Each period starts with an electron in and new highest energy shell.
Period 2 > the 2s a d 2p shells are gradually filled
Period 3 > 3s and 3p sub shell is gradually filled
Across period 4 > 4s, 3d and 4p is gradually

Question 4

Block in the periodic tables

Answer 4

The s-block > consists of groups 1 and 2
The d-block > consist of the transition metals
The p-block > consist of groups 3-8

Question 5

What is the first ionisation energy

Answer 5

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.
Na(g) —> Na+ (g) + e-

Question 6

What are the factors affecting ionisation energy?

Answer 6

• atomic radius > greater the distance between nucleus and outer electrons the less nuclear attraction.
• nuclear charge > more protons the greater the attraction between nucleus and outer electrons
• electron shielding > inner shells repel outer shells reducing the nuclear attraction.

Question 7

What does successive ionisation energy’s show?

Answer 7

• the number of electrons in the outer shell
• the group of the elements in the periodic table
• the identity of an element

Question 8

What’s the trend of first ionisation energy down a group?

Answer 8

First ionisation energy’s decrease down a group as
- atomic radius increases
- shielding increases
Resulting in nuclear attraction decreasing.

Question 9

Trends in fist ionisation energy across a period?

Answer 9

First ionisation energy increases across a period as
- nuclear charge increases (extra proton)
- similar shielding
-atomic radius decreases
Meaning nuclear attraction increases.

Question 10

What causes the first fall between beryllium to boron in first ionisation energy?

Answer 10

It marks the start of filling the 2p sub-shell. Has the 2p sub-shell is a higher energy shell borons 2p electron is easier to remove.

Question 11

What caused the fall in first ionisation energy between nitrogen and oxygen?

Answer 11

It makes the start of electron pairing. The paired electrons in oxygen repel each other making it easier to remove the outer electron.

Question 12

What is a metallic bond?

Answer 12

Metallic binding is the strong electrostatic attraction between the positive metal ions (cation) and the delocalised electrons.

Question 13

How does a metallic bond form?

Answer 13

In a sold metal structure each metal atom donates its outer electrons creating a sea of delocalised electrons and a positive metal ion.
It creates a fixed lattice structure.

Question 14

Properties of metals

Answer 14

Most metals have
- high electrical conductivity
- high melting and boiling points
- insoluble

Question 15

Electrical conductivity of a metal

Answer 15

Metals conduct electricity in solid and liquid states as the delocalised electrons can move through the stature carrying a charge and acting as a mobile charge carrier.

Question 16

Melting and boiling point of a metal?

Answer 16

Most metals have high melting and boiling points. As a high amount of energy is needed to overcome the strong electrostatic attraction.

Answer 17

Ddd

Question 18

What are giant covalent structure?

Answer 18

Many non-metal elements exist is a simple covalently bonded molecule. In a solid state this molecules form a lattice structure held together by weak intermolecular forces.

Question 19

What is a giant covalent lattice?

Answer 19

The non-metals boron, carbon and silicon can form structures held together by a network of strong covalent bonds forming a giant covalent lattice.
E.g. diamond and graphite

Question 20

What are the properties of a giant covalent lattice and why?

Answer 20

High melting and boiling points > high amounts of energy is needed to overcome the strong covalent bonds
Insoluble > the covalent bonds are far to strong to be broken by interactions with solvents.
No electrical conductivity > no free mobile charge carrier (except graphene)

Question 21

What is graphene?

Answer 21

A single layer of graphite, composed of hexagonally arranged carbon atoms linked by strong covalent bonds.

Question 22

What is graphite?

Answer 22

Composed of parallel layers of hexagonally arranged carbon atoms. The layers are bonded by weak London forces. The bonding only used 3 electrons resulting the the 4th one to be delocalised and able to move around the structure, allowing it to conduct electricity.

Question 23

Why does melting point vary across a period?

Answer 23

The variation in melting point is due to the change from giant metallic structures to giant covalent stature to simple molecular structures.