AS periodicity + structure Flashcards
How is the periodic table arranged?
In atomic numbers , groups and periods
3 factors affecting ionisation energies
- Nuclear charge - ↑ proton = ↑ attraction
- Atomic radius - ↑ dist. = ↓ attraction
- Shielding - ↑ shells = ↑ repulsion
What stays relatively constant throughout the period
Atomic radius and shielding
3 exceptions to the steady ↑ in
ionisation energy across period
- group 2 -> 3
- group 5 -> 6
- increase in period
Why is their a dip in ionisation energy between
group 2 -> 3 ?
(3 points)
electron removed is going from 2s -> 2p
↑ in atomic radius = ↓ attraction
Why is their a dip in ionisation energy between group 5 -> 6 ?
Group 5 has 3 electrons in 2p orbital
Group 6 has 4 electrons in 2p orbital
↑ repulsion at Group 6 as electron shares orbital
Why is there a dip in ionisation energy when going from down period?
- ↑ atomic radius
- ↑ shielding
- both factors outwiegh ↑ nuclear charge
What is the pattern in ionisation energies down the group + WHY?
↓ down the group
1. gain a shell
2. shielding increases
3. atomic radius increases
4. both factors outweigh increased nuclear charge
How to predict group through successive ionisation energies ?
A peak in ionisation energies = no. of electron in outershell = group no.
Definition of ionisation energy
Energy required to remove 1 mol of electrons from 1 mol of gaseous atoms to form 1 mol of gaseous 1+ ions
Define Metallic bonding
The electrostatic attraction between metal cation and sea of delocalised electron
What is the structure of all metal ?
A gaint metallic lattice structure
4 Properties of metallic srtucture
- ↑ MP and BP
- ↑ electrical conductivity
- Insoluble
- malleable
Define gaint covalent structure
A network of atoms bonded by strong covalent bond
Properties of gaint covalent structure
- high M.P. and B.P.
- Insoluble
electrical conductivity of graphite and diamond
Graphite - conducts
[only 3 covalent bond/carbon,1 mobile]
Diamond - Doesn’t
[ 4 covalent bonds, no mobile electron]
describle the trend of B.P. across period
Group 1-4 = gradual increase [gaint structure]
Group 4-5 = sudden drop
group 5-8 = neglictible difference [simple molecular]
Reactivity of group 2 down the group
INCREASES
1. ↑atomic radius
2. ↑shielding
3. ↓energy required to remove an electron
What happens when group 2 reacts
oxidised to form 2+ ions
What do Group 2 form when reacted to water
metal hydroxide and hydrogen
how does solubility changes down the group 2 ? and WHY?
INCREASES solubility and pH
1. As they are more reactive down the group
2. particles are more likely to be attracted to polared molecules
3. hence more soluble
how does pH changes down the group 2 ? and WHY?
INCREASES1. as they are mroe soluble down the group 2. more group 2 oxides reacts and form more OH ions 3. hence conc of OH increases
What is the action of water on group 2 oxides
metal oxides + water -> metal 2+ + 2 OH -
2 uses of group 2 compounds
- milk of magnesia (Mg(oH)2) - neutralise stomach acid
- Calcium hydroxide neturalise acidic soil
What do all pure halogens exists in?
diatomic molecules
Trend of BP down the group 7?
Increases down the group
1. ↑ no. of electrons
2. ↑ London forces
3. ↑ electrons = ↑ london forces
Color of halogens in water
Cl - pale green
Br - orange
I - brown
which halogen have a different colour in organic solvent and what colour ?
In cyclohexane : Iodine - violet
Reactivity of Halogens down the group
Decreases
1. ↑ atomic radius’
2. ↑ shielding
3. ↓ nuclear attraction to GAIN ELECTRON
Rule for halogen displacement
More reactive displaces less reactive
formulae for Bleach
NaClO
formula for choric acid
HClO
Pros and cons of use of Chlorine in water treatment
Pros
* kills bacteria (e.g. Cholera)
Cons
* irritant in small amount
* fatal in large amounts
* chlorinated hydrocarbon may form
How does atomic radius increases
down and left
How does 1st ionisation increases across period?
+ explain (4)
- ↑ nuclear charge
- dist. from nucleus = k
- shielding = k
- ↓ atomic radius
↑ attraction so ↑
Colour of iodine in solution
Yellow - orange
Colour of bromine in solution
Orange
Colour of chlorine in solution
Pale green
