Redox and Groups chemistry

Diatomic elements

Diatomic elements

HON 7 (hydrogen, oxygen, nitrogen, group 7)

What is a redox equation

When oxidation and reduction occur simultaneously

What is oxidation

gain of oxygen

loss of electrons

What is reduction

gain of electrons

loss of oxygen

what is an oxidizing agent

a substance that oxidizes another species (substance) and itself is reduced

what is a reducing agent

a substance that reduces another species (substance) and itself is oxidized

Alkali metal properties

• Low mp and bp

• soft - cut through with a knife, inside tarnishes when exposed with air and forms dull coatings of metal oxide so its stored in oils

• low density

• react with water produce metal hydroxide and hydrogen

• valency 1, form 1+

• 1 e- on outer shell

alkali metal white compound produces what

colourless solutions

What do alkaline metal oxides produce when reacted with water

soluble alkaline hydroxides

What is the trend in alkai metals

mp and bp decreases down the group because the metallic bonding get weaker so less energy is needed to break the bonds

softness increases down the group

general (not all) increase in density down the group

increase in reactivity down the group

What are group 1 elements

alkali metals

alkali metal + water →

alkali hydroxide + hydrogen gas

alkali metal + oxygen →

alkali metal oxide

Why is there an increase in reactivity down group 1

Down the group there are more shells so the distance between the nucleus and outer shell is increases.

Therefore the attraction is weaker and electrons are lost more easily.

Group 1 elements lose electrons and so they are reactive

reactive meaning

how easily an element loses or gains e-

What are group 7 elements called

halogens

when does an element displace another element

when they are more reactive then the other

Trend down group 7

• reactivity decreases down the group

• mp and bp increase

• poor conductors

trend in halogen displacement reaction

more reactive halogen is reduced, less reactive halide ion gets oxidised

properties of halogens

• exist in pairs - diatomic

• simple molecular structure

• intermolecular forces between molecules

• 2e- on outer shell so 2+ charge ion forms

Why does the mp and bp increases down 7

as you go down the Mr of molecules increases causing the strength of the intermolecular forces to increase and so more energy is needed to break the these forces

Why do halogens react in a similar way

same number of outer shell e-

outer e- determines the type of reaction

Why does reactivity increase with less shells if an element is prone to gaining e-

with less shells, incoming e- are closer to the nucleus and therefore more strongly attracted by the nucleus and easily gained

What are group 8 or group 0 elements

noble gases

Properties of noble gases

• non-metal

• monoatomic (exist as single atoms)

• colourless

• non-flammable at room temp

• unreactive

• glow when high voltage is applied

• less dense than air

why are noble gases inert (unreactive)

don’t form ions because they have a full outer shell

why is better to say group 0 than group 8

not all noble gases have 8 e- on their outer shell

what property makes noble gases useful

their inertness is useful

what are noble gases used for

• helium in balloons because it doesn’t burn, less dense than air

• neon, argon and xenon used in advertising signs

  - they glow brightly when high voltage applied to gas

• argon in light bulbs - if filled with a reactive gas it would reactive with the metal filament when it gets hot and the metal would corrode

• helium for airships - wouldn’t catch on fire

• argon for welding - metals get hot and do not corrode

trend in group 0

bp increases down the group because intermolecular forces get stronger as the Ar of the atom increases - more energy is needed to break the forces

density down the group increases

Transition metal properties

• malleable

• ductile

• conductors

• shiny when polished

• high mp and bp

• high density

• compounds form coloured compounds

• catalysts

Why do transition metals form coloured compounds

they form multiple ions with different charges, this causes the colour change

the element by itself is just a grey metal colour

Iron uses

• catalyses the manufacture of ammonia in the Haber process

• compounds of iron (iron(iii)chloride) catalyses the manufacture of poly(chloroethene)

• low carbon steel in car bodies as they are malleable

• high carbon steel in construction of buildings/bridges due to strength

what is an alloy

a metal made from mixing 2 or more metals together or a metal and another substance

what is iron alloyed with

iron + carbon = steel (more carbon = stronger steel)

iron + chromium = stainless steel

iron + nickel = stainless steel (resistant to corrosion)

Gold properties

• malleable

• unreactive

• resists corrosion

gold uses

• jewellery (unreactive)

also alloyed with silver, copper, zinc to make jewellery stronger

How is gold measured

carats, 24 carats is pure gold