Elements of Life: Periodicity

Question 1

elements are classified as s, p or d block according to what

Answer 1

According to which orbitals the highest energy electrons are in

Question 2

How do u work out which elements are in which block

Answer 2

• groups 1-2 = s block
• groups 5-8 = p block
• transition metals = d block

Question 3

What does the period tell you ( electronic configuration )

Answer 3

The last biggest number in the electronic configuration ( the no. of shells )

Question 4

As you go across within in a block what increases

Answer 4

The number of electrons within that subshell

Eg. 3rd column along in p block will =
p3 ( 3 electrons in subshell p )

Question 5

Definition of periodicity

Answer 5

Pattern in properties across a row which is repeated in each row

Question 6

As you go across the period what happens to the atomic radius ( size of atom )

Answer 6

Atomic radius decrease ( atom gets smaller )

Question 7

Why does atomic radius decrease ( atoms get smaller ) as you go across the period (3)

Answer 7

1. More protons ( greater positive charge )
2. Outer electrons in same shell
3. Stronger pull due to more protons pulling the electrons closer to the nucleus

( = decrease size as electrons pulled )

Question 8

What happens to atomic radius ( size of atom ) as you go down a group

Answer 8

Atomic radius increase ( atom gets bigger )

Question 9

Why does atomic radius increase ( atom get bigger ) as you go down the group (2)

Answer 9

1. More electrons

2. More electron shells

Question 10

Definition of 1st ionisation energy

Answer 10

Enthalpy change ( energy required ) to remove 1 electron from each atom in a mole of gaseous atoms

Question 11

Equation for 1st ionisation energy

Answer 11

X(g) —> X+ (g) + e-

Question 12

Equation for 2nd ionisation energy

Answer 12

X+ (g) —> X2+ (g) + e-

Question 13

What is the general trend across the period for ionisation energy

Answer 13

Ionisation energy increases

Question 14

Why does ionisation energy generally increase across the period (3)

Answer 14

1. More protons ( more +be charge )
2. Smaller atoms
3. Stronger attraction from nucleus to outer shell

Question 15

If the ionisation energy is high or low what does it mean

Answer 15

High = hard to remove outer electron

Low = easier to remove outer electron

Question 16

What is the general trend down a group for ionisation energy

Answer 16

Ionisation energy decreases

Question 17

Why does ionisation generally decrease as you go down the group ( 3 )

Answer 17

1. More shells
2. Distance between nucleus + outer shell increases
3. More shielding ( from larger no. of inner electrons

= attraction between nucleus and outer electrons decreases

Question 18

What 3 factors effect ionisation energy

Answer 18

1. Nuclear charge - more protons = stronger= higher ionisation energy
2. Distance from nucleus- attraction decease with distance = larger distance = weak attraction = low ionisation energy
3. Shielding- more shells = more shielding = weaker attraction= low ionisation energy

Question 19

What is the exception of general ionisation energy in terms of group 2-3

Answer 19

??? Group 3 has a lower ionisation than 2 ( eg Al higher than Mg )

Question 20

Why does group 3 have a lower ionisation energy than group 2

( i.e. a dip in the graph )

Answer 20

??? Shielding effect
Group 2 = s orbital
Group 3 = p orbital

P orbital higher energy level than s orbital = further away from nucleus = more shielding = weaker attraction to nucleus = easier to remove outer electron = lower ionisation energy

Question 21

What is the exception of general ionisation energy in terms of group 5-6

Answer 21

??? Group 6 has a lower ionisation energy than group 5 ( although would expect to higher )

Eg. S is lower than P

Question 22

Why does group 6 have a lower ionisation energy than group 5

( i.e. a dip in the graph )

Answer 22

???
Group 5 = final orbital only has 1 electron

Group 6 = final orbital has 2 electrons

Additional repulsion between newly paired up electrons = lower ionisation energy

Question 23

Definition of electronegativity

Answer 23

Power of an atom to attract the 2 electrons in a covalent bond

Question 24

Compare H2 and HCl

- which molecule has a higher electronegativity

Answer 24

HCl

Cl = 17 protons 
H = 1 proton 

Cl is 17x more +ve = has greater power to attract electrons in covalent bond than H

( on diagram the electrons will be closer to Cl than H where as in H2 electron in middle because strength is equal )

Question 25

What is the general trend of electronegativity across the period

Answer 25

Electronegativity increases as you go across the period

Question 26

Why does electronegativity generally increase as you go across the period (3)

Answer 26

1. More protons
2. Smaller atoms
3. stronger attraction from nucleus to 2 electrons in covalent bond

Question 27

What kind of melting/ boiling point do metals have eg. Na, Mg and Al

Answer 27

High melting / boiling point

Question 28

Why do metals have high melting/ boiling points

Answer 28

Strong metallic bonding

- electrostatic attraction between +ve ions and -ve delocalised electrons

Question 29

What is the general trend for melting / boiling point of metals across the period and why

Answer 29

Increases

• smaller ions
• higher charge (on metal ion)
• more delocalised electrons

Question 30

What is the general trend for giant covalent melting/ boiling points eg. Si ( Silicon ) and why

Answer 30

Very high melting/ boiling point

• giant covalent structure
• requires larger amount of energy
• to break many strong covalent bonds

Question 31

What is the general trend of melting / boiling point for simple molecular

Answer 31

Low melting/boiling point

- simple molecular = weak van Der Waals ( intermolecular) forces

Question 32

What is the general rule for atoms with Van Der Waal forces ( simple molecular ) eg. S8, P4, Cl2

Answer 32

The molecule with more electrons will have strong van Der Waal forces

Eg. With given examples above S8 = most strong =higher melting / boiling point

Question 33

What is the general trend for melting/ boiling point for monatomic elements and why

Answer 33

Very low melting / boiling point

- very weak Van Der Waal forces