Periodicity Flashcards
Ionisation energy
Energy required to remove an electron from each atom in one mole of gaseous atoms to for one mole of gaseous +1 ions
Factors affecting ie
Atomic radius-greater less energy req
Nuclear charge- more protons more energy required
Electron shielding- inner shell repel outer shell increase radius less energy
Successive ionisation energies
Large increase in ie suggests the number of electrons in its outer shell
Due to the shielding being less and smaller radius
Ionisation energy group
Decreases down a group
Atomic radius incr
Shielding increases
Nuclear attraction decreases
Ionisation energy across a period
Increases
Nuclear charge incr
Nuclear attraction incr
Atomic radius decrease
Falls in ie across a period
Group 3 and group 6
3= filling 2p sub shell easier to remove from p than 2s
6= paired electron in a 2p orbital repel each other easier to remove than single electron
Periodic trend in melting points
Across period increase form group 1 to 4 (giant structures metallic/covalent)
Sharp decrease from 4 to 5 (drop to simple molecular)
5 to 8 low mp
Group 2 reactions
Reducing agent (lose 2e-)
Redox with oxygen forming oxide
Redox with water forms hydroxide
Redox w dilute acid (metal salt)
Group 2 reactivity trend and ie
IE decreases down the group
More reactive and stronger reducing agents down the group
Reaction of group 2 compounds
Oxides react with H2O form hydroxide ions
When saturated form hydroxides
Solubility of these hydroxides increase down group as well as pH
Uses of group 2 compounds
Hydroxides Ca(OH)2 added to field to increase pH of acidic soils
Group 2 bases used as antacids for indigestion mainly carbonates are used
Mg(OH)2 is sometimes used
Halogen trends
Boiling point increases down group due to more electrons so stronger London forces
Reactions of halogens
Redox reactions lose 1e- from atom oxidising agent
Displacement reactions
Displacement reactions
Cl2 displaces Br- and I- forms orange and violet
Br2 displaces I- forms violet solution I2 in cyclohexane
Halogen reactivity tren
Decreases down the group as atomic radius increases so less nuclear attraction to capture electron from other species
Disproportionation
when one species is oxidised and reduced in the same reaction equation
Cl2 and water forms HClO and HCl
Cl2 with NaOH forms NaClO and NaCl
Chlorine use
Chlorine kills bacteria in water sources
However is extremely toxic and is a respiratory irritant
Chlorine can react with methane to form chlorinated hydrocarbons which can cause cancer
Test for anions
Carbonate test
Sulfate test
Halide test
Carbonate test
Add to dilute nitric acid
If bubble carbonate could be present if like water cloudy carbonate was present
Sulphate test
Ba2+ ions added as BaCl2 or BaNO3
Barium sulphate is very insoluble in solution
if SO4 present white pp forms
Halide tests
Add silver nitrate
Cl- is white Br- is cream I- is yellow
Cl- is soluble in dilute NH3
Br- is soluble in conc NH3
I- is insoluble in conc NH3
Sequence of tests
- Carbonate
- Sulphate- barium carbonate is also white and insoluble
- Halides-silver carbonate and sulphate are also insoluble in water and forms pp
