2.1 Periodicity

Question 1

How are elements in the periodic table arranged?

Answer 1

By proton number

Question 2

What is a period on the periodic table?

Answer 2

The horizontal rows

Question 3

What are groups on the periodic table?

Answer 3

The vertical columns

Question 4

What does the group number indicate on the periodic table

Answer 4

The number of outer electrons of an element

Question 5

What are the 4 blocks of the periodic table?

Answer 5

S-block
P-block
D-block
F-block

Question 6

What elements are in each block of the periodic table?

Answer 6

S-block: groups 1 and 2
P-block: groups 3 to 0
D-block: transition metals
F-block: radioactive elements

Question 7

What is periodicity ?

Answer 7

The study of trends within the periodic table. Often these trends are linked to elements electronic configuration

Question 8

What is the trend in atomic radius along a period?

Answer 8

Decreases

Question 9

Why does atomic radius decrease across a period?

Answer 9

Atomic radius decreases due to an increased nuclear charge for the same number of electron shells
This means that the outer electrons are pulled closer to the nucleus because the charge produces a greater attraction
As a result the atomic radius is reduced

Question 10

What is the trend of atomic radius going down a group?

Answer 10

Increases

Question 11

Why does atomic radius increase going down a group

Answer 11

With each increment down the group an electron shell is added
This increases the distance between the outer electrons and nucleus, reducing the power of attraction
More shells also increases electron shielding, whereby the inner shells create a ‘barrier’ that blocks the attractive forces
The nuclear attraction is reduced further and the atomic radius increases

Question 12

What is the trend in ionisation energy along a period

Answer 12

Increases

Question 13

Why does ionisation energy increase along a period

Answer 13

It increases because atomic radius decreases, hence nuclear charge increases
This means that the outer electrons are held more strongly so more energy is required to remove the outer electron and ionise the atom

Question 14

What is the trend in ionisation energy going down a group

Answer 14

Decreases

Question 15

Why does ionisation energy decrease going down a group

Answer 15

The nuclear attraction between the nucleus and outer electrons reduces and shielding increases. Both of these factors mean less energy is required to remove the outer electron

Question 16

What does the melting point of Period 3 elements depend on?

Answer 16

The structure of the element
The bond strength

Question 17

What happens to melting points across Period 3 between sodium and aluminium?

Answer 17

Sodium, Magnesium and aluminium are all metals with metallic bonding.
Their melting points increase due to greater positive charge of their ions
This means more electrons are released in the form of free electrons
This increases the electrostatic attractive forces from Na to Al, therefore more energy is needed to break them

Question 18

Why does the melting point increase dramatically for silicone in Period 3?

Answer 18

Silicon has a very strong covalent structure
So more energy is required to break the strong covalent bonds giving it a very high melting point

Question 19

Why does the melting point decrease in Period 3 between Phosphorus and Chlorine

Answer 19

Phosphorus, Sulphur and Chlorine are all simple molecules held with weak Van de Waals forces
Less energy is needed to overcome these weak intermolecular forces, so these molecules have relatively low melting points

Question 20

Why does argon have an even lower melting point than Chlorine

Answer 20

Argon is a noble gas that exists as individual atoms with a full outer shell of electrons
This makes the atom very stable and Van de Waals forces between them very weak
As a result less energy is needed to overcome these weak Van de Waals forces and so argon exists as a gas at room temperature

Question 21

8.1 Q1) From the elements Br, Cl, Fe, K, Cs and Sb pick out:
i. In the same period
ii. In the same group
iii. That are non metals

B) one element
i. That is in the d-block
ii. That is in the s-block

Answer 21

i. Any two from Br, K and Fe
ii. Br and Cl or K and Cs
iii. Br, Cl

B) i. Fe
ii. K or Cs

Question 22

8.1 Q2) From the elements: Tl, Ge, Xe, Sr, and W
A) a noble gas
B) the element described by Group 4, Period 4
C) an s-block element
D) a p-block element
E) a d-block element

Answer 22

A) Xe
B) Ge
C) Sr
D) Ge or Xe
E) W

Question 23

8.2 Q1) Whereabouts in a period do you find the following? Choose from left, right or middle
A) elements that lose electrons when forming compounds
B) elements that accept electrons when forming compounds

Answer 23

A) Left
B) Right

Question 24

8.2 Q2) In what group do you find an element that exists as the following?
A) separate atoms
B) a macromolecule

Answer 24

A) 0 or 8 (or 18)
B) 4

Question 25

8.2 Q3) A and B are both elements. Both conduct electricity - A well, B slightly. A melts at a lower temperature, B at a much higher temperature
Suggest the identity of A and B and explain how their bonding and structure account for their properties

Answer 25

A: Na
B: Si

Question 26

8.3 Q1) What happens to the size of the atoms as you go from left to right across a period? Choose from increase decrease and no change

Answer 26

Decrease

Question 27

8.3 Q2) What happens to the first ionisation energy as you go from left to right across a period? Choose from increase decrease and no change

Answer 27

Increase

Question 28

8.3 Q3) What happens to the nuclear charges of the atoms as you go from left to right across a period?

Answer 28

Increase

Question 29

8.3 Q4) Why do the noble gases have the highest first ionisation energy of all elements in their period?

Answer 29

Because they have the highest nuclear charge

Question 30

8.4 Q1) Write the electron arrangement in the form of 1s2….for:
A) beryllium
B) Boron

Answer 30

A) 1s2 2s2
B) 1s2 2s2 2p1

Question 31

8.4 Q2) If one electron is lost from each of the following atoms, which main level does it come from?
A) beryllium
B) boron

Answer 31

A) 2s
B) 2p

Question 32

8.4 Q3) Why is the first ionisation energy of boron less than that of beryllium?

Answer 32

Level 2p is of higher energy than 2s

Question 33

8.3 The discovery of Argon
1) To how many significant figures were the two densities measured? (N2 = 1.2505g/dm3 from reaction and 1.2572 g/dm3 from removing O2 and CO2
2) using relative atomic masses from the periodic table, explain why Argon is denser than Nitrogen
3) suggest how oxygen could be removed from a sample of air
4) what would be the Mr of N3 to the nearest whole number?
5) Suggest why chemists were reluctant to regard argon as an element

Answer 33

1) 5
2) Ar of argon is 50% greater than that of nitrogen and 1 mole of any gas occupies the same volume
3) Pass the air over a heated metal e.g. Copper
4) 42
5) It did not fit into the periodic table as it was understood then

Question 34

9.1 Q1) What is the oxidation number of all group 2 elements and their compounds
B) Explain your answer

Answer 34

A) +2
B) They all lose their two outer electrons when they form compounds