5.
Periodic table
1. Structure of periodic table
a. List of elements
i. Arranged in order of increasing atomic number
b. Period
i. = row
ii. = number of occupied electron shells
iii. Atoms in the same period have similar sizes
c. Group
i. = column
ii. = number of electrons in outer-shell
iii. Elements in the same group have similar chemical properties
d. Metals…
i. … are found to the left of the zig-zag
ii. … conduct electricity
iii. … are malleable
iv. … have alkaline oxides
e. Non-metals…
i. … are found to the right of the zig-zag
ii. … do not conduct electricity (except graphite)
iii. … have acidic oxides
2. Group 1 (the alkali metals)
a. Reaction with water
i. Produce metal hydroxide (aq) and hydrogen (g)
e.g. 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
ii. Observations: metal disappears, effervescence
iii. Solution produced is alkaline: turns UI blue
3. Group 7 (the halogens)
a. Physical state and appearance
i. Fluorine: very pale yellow gas
ii. Chlorine: pale green gas
iii. Bromine: brown liquid
iv. Iodine: grey solid
v. Astatine: black solid
b. Halogen vs. halide
i. Halogen = diatomic element, ___ine, with 7e- in outer-shell
e.g. Br2 = bromine, 7e- in outer-shell for individual Br atom
ii. Halide = ion formed when halogen gains an ee.g. Br- = bromide, 8e- in outer-shell
c. Acidity of hydrogen chloride…
i. … dissolved in water: dissociates, releases H+ which makes solution acidic
ii. … in methylbenzene: no dissociation so no H+, solution remains neutral
d. Reactivity trend: less reactive down the group
i. More shells
ii. Outer-shell is further from the nucleus
iii. Electron to be gained has weaker attraction to nucleus
iv. Electron is therefore less easily gained
e. Displacement reactions
i. Colours:
All halide compounds are colourless.
Cl2(aq) is colourless
Br2(aq) is yellow
I2(aq) is brown
ii. More reactive halogens displace less reactive halogens from solution
e.g. Cl2(aq) + 2KBr(aq) → 2KCl(aq) + Br2(aq)
iii. Observations:
1. Bromine produced: colour changes to yellow
2. Iodine produced: colour changes to brown
iv. Redox: the halogen is reduced (gains e-), the halide is oxidised (loses e-)
Shown using ionic equations:
Cl2(aq) + 2Br-(aq) → 2Cl-(aq) + Br2(aq)
Cl2(aq) + 2I-(aq) → 2Cl-(aq) + I2(aq)
Br2(aq) + 2I-(aq) → 2Br-(aq) + I2(aq)
4. Oxygen
a. Gases in air
i. 78% nitrogen
ii. 21% oxygen
iii. 1% argon
iv. 0.04% carbon dioxide
v. Determining % oxygen: remove the oxygen by reaction with a metal (e.g. Cu),
measure volume reduction from 100cm3 to 79cm3 (-21%)
b. Lab preparation by decomposition of hydrogen peroxide
i. 2H2O2 → 2H2O + O2
ii. Manganese dioxide (MnO2) catalyst
iii. Collect O2 under water or in gas syringe
c. Reaction with elements
i. Form one oxide only
e.g. 2Mg(s) + O2(g) → 2MgO(s)
ii. Bright white light with Mg
iii. Blue flame with S
iv. Metal oxides are alkaline, non-metal oxides are acidic
d. Reaction with compounds
i. Form one oxide for each of the elements in the compound
e.g. N2H4 + 3O2 → 2NO2 + 2H2O
e. Combustion of hydrocarbon fuels in oxygen
i. Produces sulphur dioxide from sulphur impurities
ii. Produces nitrogen oxides from nitrogen in the air
iii. Both cause acid rain, which kills trees and aquatic life and destroys buildings:
5. Carbon dioxide
a. Lab preparation from calcium carbonate and dilute hydrochloric acid
b.
c.
d.
e.
i. CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
ii. Collect CO2 under water or in gas syringe
Formation by thermal decomposition of metal carbonates
i. metal carbonate → metal oxide + carbon dioxide
e.g. CuCO3(s) → CuO(s) + CO2(g)
Physical properties and uses
i. Slightly soluble: used in carbonated drinks
ii. Denser than air: used in fire extinguishers
Forms acidic solutions of H2CO3 (carbonic acid)
CO2 + H2O  H2CO3
Contributes to the greenhouse effect, which definitely causes global warming and may
cause climate change
6. Water
a. Formed by combustion of hydrogen
i. 2H2 + O2 → 2H2O
ii. Lit splint  squeaky pop, which is the chemical test for H2
b. Chemical tests: to show the presence of water
i. Anhydrous copper sulphate: white → blue
ii. Anhydrous cobalt chloride: blue → pink
c. Physical tests: to show the purity of water
i. MP = 0°C
ii. BP = 100°C
iii. More accurate data = more pure water
7. Group 8 (the noble gases)
a. Monatomic elements
b. All gases at room temperature and pressure
c. Chemically inert (unreactive)
i. They have full outer-shells
ii. So are already stable