Chemistry of the Elements Flashcards
Metals in the period table:
On the left of the zig zag
Conduct electricity - allow charge to pass through them
Metal oxides are BASIC and will neutralise acids. metal oxides which dissolve will form alkaline solutions (pH more than 7)
Define group and period?
Periods are the rows (properties change as you go along)
Groups are the columns (similar chemical properties - same number of electrons on outer shell, properties such as reactivity gradually change as you go down - atomic number increases)
Non- metals of the periodic table:
Right of the zig zag
poor conductors of electricity
non-metals are acidic. They dissolve in water to form solutions with a pH of less that 7.
Why are noble gases inert? (Group 0/8)
Don’t react with anything because they have a full outer shell of electrons. They are not desperate to gain or lose electrons.
Group 1 is called and why?
The Alkali metals react vigorously with water to produce a metal hydroxide solution, which is alkaline, and hydrogen (fizzing happens).
Reaction for sodium and water:
Sodium + water —> sodium hydroxide + hydrogen
2Na(s) + 2H2O(l) —> 2NaOH (aq) + H2(g)
Moves around surface, hissing sound, bubbles of gas, melts into shiny ball, gets smaller and smaller until disappears
Reaction for lithium and water:
Lithium + water —> lithium hydroxide + hydrogen
2Li(s) + 2H2O(l) —> 2LiOH (aq) + H2 (g)
Moves around surface, hissing sound, bubbles of gas, smaller until disappears
Reaction for potassium and water:
Potassium + water —> potassium hydroxide + hydrogen
2K(s) + 2H2O (l) —> 2KOH(aq) + H2 (g)
Moves around surface, hissing sound, bubbles of gas, melts into a shiny ball, bubbles with lilac flame, gets smaller and smaller until disappears
Describe the relative reactivities of the elements in Group 1
As you go down, they become more reactive
you can see this with their water reactions - the time taken for a lump of the same size of each element to react completely with water and disappear decreases down the group (lithium takes longer than sodium and potassium is shortest time)
Explain why as you go down Group 1, it gets more reactive?
As the atomic number of the elements in group increase, reactivity increases.
They all have to lose 1 electron. The outermost electron becomes further away from the nucleus as you go down the group, which means attraction between outermost electron and nucleus becomes less, so it’s more easily lost, which means more reactive
What is the colour and physical state at room temperature of chlorine?
Green, gas
What is the colour and physical state at room temperature of bromine?
Red-brown, liquid
What is the colour and physical state at room temperature of iodine?
Dark grey, solid
Explain why reactivity decreases down the group for halogens?
As the atomic number of the elements in group increase, reactivity decreases.
They all have to gain 1 electron. The outer shell of electrons becomes further away from the nucleus as you go down the group as there are more shells in between, which means attraction between outer shell and nucleus becomes less, so it’s harder and slower to attract another electron, therefore it’s less reactive.
However at the top of the group, with less shells, the outer shell is close to the nucleus so the pull from the nucleus is greater. (Fluorine most reactive)
What’s the difference between Hydrochloric acid and hydrogen chloride?
Hydrogen chloride is hydrogen combined with chlorine which is a gas at room temperature (HCl)
When hydrogen chloride is dissolved in water, the HCl molecules split up into H+ ions and Cl- ions (this is called dissociation). Hydrochloric acid contains H+ ions so is an acidic solution. (Blue litmus paper would turn red/pink)
Why is hydrogen chloride acidic in water but not in methylbenzene?
When dissolved in an organic solvent like methylbenzene, it doesn’t dissociate into H+ ions and Cl- ions. Not acidic as there are no H+ ions.
(Solution of HCl in methylbenzene with blue litmus paper - stay blue! But if any moisture on paper or in bottle, HCl will dissociate and behave like an acid again.)
Make predictions about the properties of other halogens in this group:
We would expect:
the colour to get darker down the group.
the melting and boiling points to keep getting higher further down the group.
Describe displacement experiments with the halogens:
Add a few drops of halogen solution/ halogen water (chlorine/bromine/iodine water) to the salt solution (potassium chloride/bromide/iodide solution-colourless)
Chlorine is most reactive so with bromide solution will displace bromine and become potassium chloride (Orange solution- bromine is formed), with potassium iodide will become potassium chloride (brown solution - iodine formed)
Bromine is more reactive than iodine and less than chlorine. With potassium iodide it will form potassium bromide (brown solution- iodine formed)
➡️ a halogen will displace a less reactive halogen for an aqueous solution of its halide
Understand displacement reactions as redox reactions:
In displacement reactions, the halogen molecule is gaining an electron - being reduced.
X2 + 2e- —> 2X-
The halide ions are losing electrons - being oxidised
2Y- —> Y2 + 2e-
Both reduction and oxidation are taking place - redox reaction
Chlorine displacing iodine, bromine:
Bromine displacing iodine:
Cl2 + 2e- —> 2Cl (reduction)
2 Br- —> Br2 + 2e- (oxidation)
Cl2 + 2e- —> 2Cl (reduction)
2 I- —> I + 2e- (oxidation)
Br2 + 2e- —> 2Br (reduction)
2 I- —> I + 2e- (oxidation)
Everything is (aq)
What are the approximate percentages by volume of the gases in air?
Nitrogen 78%
Oxygen 21%
Argon 0.9%
Carbon dioxide 0.04%
(Can be a lot of water vapour too)
What’s an oxidising agent?
One that accepts electrons and gets reduced
What’s a reducing agent?
One that donates electrons and gets oxidised
Describe an experiment to investigate the proportion of oxygen in the atmosphere with copper:
Copper reacts with oxygen in the air when heated to make copper (II) oxide (reaction uses up oxygen)
- hear an excess of copper in a tube and pass air over it using two syringes, you can use the markers on the syringes to tell you how much oxygen has been used up
- start with 100cm3 of air, you’ll end up with 80cm3 when the reactions finished and the air has cooled. (around 20% if he air must be oxygen)
2Cu + O2 —> 2CuO
