Alkali Metals Group 1 + Halogens Group 7 Flashcards
Why are alkali metals highly reactive (2 reasons)
Because they only have one electron in the outer shell
And have a large atomic radius so electrons are held less strongly to thr positive nuclei (because further away from positive nucleus)
Do alkali metals have low or high boiling/melting points and explain why?
Low boiling/melting point
Because electrons in the outer shell are held weakly to the positive nuclei due to its large atomic radius
So electrostatic forces of attraction are weaker so less energy is required to break the bonds
(between the sea of delocalized electrons and the positive nuclei)
Do alkali metals have low or high densities? Can any float on water?
Low densities
Lithium, sodium potassium can float
Why do alkali metals all have similar properties
Because they have one electron in their outershell
Give two physical properties of alkali metals
Shiny when freshly cut but quickly tarnish
Soft to cut with a knife
What kind of solution do all alkali metals form with water
Alkaline solutions
What is the word equation for an alkali metal with water
Alkali metal + water —-) metal hydroxide + hydrogen
Write the balanced symbol equation for the reaction between potassium and water with state symbols
2K(s) + 2H20———) 2KOH(aq) + H2(g)
Give two properties of all metal hydroxide solutions
Aqeous
colourless
Write the balanced symbol equation with state symbols of reaction between Lithium and water
2Li(s) + 2H20(l) ——-) 2LiOH(aq) + H2(g)
Describe 4 observations from the reaction of lithium and water and explain why they happen(4)
- fizzes steadily because hydrogen is given off
- Lithium does not melt
- Relatively slow reaction
- eventually dissapears
Describe four observations from the reaction between sodium and water and explain why (3)
- Fizzes rapidly
- Melts to form a ball( because a lot of heat is released)
- ball moves across the surface (because hydrogen catches fire) and eventually dissapears
Describe 5 observations from the reaction between potassium and water and explain why (5)
- fizzes very rapidly
- Melts into a shiny ball- because a lare amount of heat is released
- dashes quickly across the surface - because hydrogen catches fire
- Burns to form a lilac flame- because a large amount of heat released
- sometimes there is an explosion
What kind of hazard could happen if alkali metal is in contact with water
Would be corrosive and could cause burns
Why are alkali metals stored in oil
To prevent them reacting with oxygen or water
Does the density increase or decrease down the group of alkali metals
Density increases
Why do alkali metals tarnish/corrode when exposed to air
Because they form metal oxides when reacted with oxygen
What does metal oxide look like on an alkali metal
A dull coating over the surface
Is rubidium less dense than water
No it is more dens
What is the word equation for the reaction between alkali metals and oxygen
Alkali metal + oxygen —-) metal oxide
What is the symbol equation for the reaction between sodium and oxygen with state symbols
4Na(s) + O2(g) ——-) 2Na2O(s)
What is the balanced symbol equation for the reaction between Potassium and oxygen with state symbols
4K(s) + O2(g) ——) 2K2O(s)
Predict the melting point, density and reaction between water of rubidium
Melting point is lower than potassium
Density is higher than potassium
Reacts more vigorously and explosively than potassium
Does the melting/boiling point of the halogens increase or decrease as you go down the group and explain why?
Melting/ boiling point increases
Because molecular mass increases
So the intermolecular forces of attraction become stronger
And more energy is required to break them
Does the reactivity of the halogens increase or decrease as you go down a group and explain why
Reactivity decreases
Because atomic radius gets larger of each atom
so forces of attraction between the positive nuclei and shared electrons are weaker
Why are halogens gases at the top of the group but solids at the bottom of the group
Because boiling and melting point increases as you go down so more energy is required to break the intermolecular forces of attraction
Are halogens good conductors of heat and electricty? Explain why
Poor conductors of heat and electricty
Because covalent substances
So no delocalized electrons