3.1.1 - Periodicity

Question 1

How are the elements arranged in a periodic table?

Answer 1

They are arranged in the order of increasing atomic numbers

Question 2

What is a period on a periodic table?

Answer 2

The horizontal rows in the periodic table

Question 3

What is a group on a period table?

Answer 3

The vertical columns

Question 4

What is meant by periodicity?

Answer 4

The repeating trends in chemical and physical properties

Question 5

What change happens across each period?

Answer 5

Elements change from metals to non metals

Question 6

How can the electron configuration be written in short?

Answer 6

The noble gas before the element is used to abbreviate

e.g. Li —> 1s2 2s1 ; Li ——> [He] 2s1

Question 7

Define first ionisation energy

Answer 7

The energy required to remove one mole of electrons from one mole of atoms in a gaseous state, to form one mole of 1+ ions also in their gaseous state

Question 8

Write an equation for the first ionisation energy of magnesium

Answer 8

Mg (g) —–> Mg+ (g) + e-

Question 9

What are the factors that affect ionisation energy?

Answer 9

Atomic radius
Nuclear charge
Electron shielding

Question 10

Explain the trend on this graph

Answer 10

First ionisation energy increases across period 3 because of:
increased nuclear charge
Decreased atomic radius
Same electron shielding

Which means that more energy is needed to remove the first electron

Dips at Al because:
outer electron is in 3p orbital, higher energy than 3s orbital
less energy is needed to remove electron

Dips at S because:
one 3p orbital contains 2 electrons
Repulsion between paired electrons
Less energy is needed to remove electron

Question 11

Why does first ionisation energy decrease between group 2 to 3

Answer 11

Decrease between 2 o 3 because in group 3, the outermost electrons are in p orbitals whereas in group 2 they are in s orbital, so the electrons are easier to be removed

Question 12

Why does first ionisation energy decrease between group 5 to 6?

Answer 12

The decrease between 5 to 6 is due to the group 5 electrons in p orbital are single electrons and in group 6, the outermost electrons are spin paired, with some repulsion. Therefore the electrons are slightly easier to remove.

Question 13

Does first ionisation increase or decreases between the end of one period and the start of the next? Why?

Answer 13

Decrease

There is increase in atomic radius
Increase in electron shielding

Question 14

Does first ionisation increase or decrease down a group? Why?

Answer 14

Decrease

Shielding increases —> weaker attraction

Atomic radius increases —-> distance between the outer electron and the nucleus increases —> weaker attraction

Increase in number of protons is outweighed by increase in distance and shielding

Question 15

What are the properties of giant metallic lattices? (4)

Answer 15

High melting and boiling point
Good electrical conductors
Malleability
Ductility

Question 16

What is a ductile metal?

Answer 16

The metal can be made stretched

eg. can be made into wires

Question 17

What is a malleable metal?

Answer 17

The metal can be shaped into different forms

Question 18

Describe the structure, forces and bonding in every element across period 2

Answer 18

Li and Be —–> giant metallic;
strong attraction between psoitive ions and delocalised electrons;
metallic bonding

B and C ——> giant ocvalent;
string forces between atoms;
covalent bonding

N2, O2, F2, Ne —–> simple molecular;
Weak intermolecular forces between molecules;
Covalent bonding within molecules and intermolecular forces between molecules

Question 19

Describe the structure, forces and bonding in every element across period 3

Answer 19

Na, Mg, Al —-> giant metallic;
Strong attraction between positive ions and delocalised electrons;
metallic bonding

Si ——> Giant covalent;
Strong forces between atoms;
Covalent bonding

P4, S8, Cl2, Ar —–> Simple molecular;
Weak intermolecular forces between molecules;
Covalent bonding within molecules and intermolecular forces between molecules