Module 3 - The Periodic Table And Periodicity Flashcards
What is the magnitude of an ionisation energy influenced by??
Nuclear charge
Atomic radius
Shielding
Effect of nuclear charge
The greater the nuclear charge the greater the attraction on the outer electrons
Effect of atomic radius
The further the electrons is from the nucleus, the weaker the attraction
Effect of shielding
Full inner shells of electrons exert a repelling effect on outer electrons. This reduces the attraction between the nucleus and outer electrons
Trends in first ionisation energy
Decrease down a group
Nuclear charge increases
Atomic radius increases so outer electron is further from the nucleus
Shielding increases as the number of full inner shells increases
Increase in distance and shielding outweighs the increased nuclear charge
Nuclear attraction on outer electron decreases
First ionisation energy decreases
Trends in first ionisation energy
General increase across a period
Nuclear charge increases
Atomic radius decreases so outer electron is closer to the nucleus
Shielding stays the same as electrons are added to the same shell
Nuclear attraction on outer shell increases
First ionisation energy increases
Decrease between groups 2 and 3
2p orbitals have slightly more than 2s
S electrons provide slightly greater shielding of the p electron
Less energy needed to remove outer electron despite increased nuclear charge
Decrease between groups 5 and 6
Spin pairing occurs in 2p subshell of oxygen
Paired electrons in a 2p orbital of oxygen repel each other
Less energy needed to remove outer electron despite increased nuclear charge
What is the atomic orbital
Region around the nucleus that can hold up to 2 electrons with opposite spin
General trend in the first ionisation energies of the first 11 elements
Nuclear charge increases
Atomic radius decreases
Outer electron is closer to the nucleus, shielding stays the same as electrons are added to the same shell
So ionisation energy increases across a period
Group number
Number of outer shell electrons
Period number
Number of electron shells
Periodicity
The repeating trend in physical and chemical properties across periods of the period table
Structure of a metallic lattice
Cations are in fixed positions giving the shape of the metal
Delocalised electrons are mobile and can move throughout the structure
What is a metallic bond??
A strong electrostatic attraction between a lattice of positive ions and a sea of delocalised electrons
Electrical conductivity in giant metallic lattices
Delocalised electrons can move and carry charge
Electrons will move towards the positive terminal, electrons will be supplied by the negative terminal
Melting and boiling points in giant metallic lattices
High due to large amount of energy needed to overcome the strong electrostatic attractions between positive ions and delocalised electrons
Metallic bond strength depends on number of outer shell electrons to be delocalised and charge density of the metal ion
Solubility in giant metallic lattices
All insoluble
Some will react with water
Structure of giant covalent lattices
Atoms held together in a network of strong covalent bonds forming a giant covalent lattice
Electrical conductivity of giant covalent lattices
Non-conductors, no delocalised electrons all outer shell electrons are used in bonding
Exception - graphite - delocalised electrons are present which can move
Melting points and boiling points of a giant covalent lattice
High due to the large amount of energy needed to break the many strong covalent bonds
Solubility of giant covalent lattices
All insoluble
What is a homologous series??
A series of organic compounds having the same functional group but with each successive member differing
What is the general formula??
The simplest algebraic formula for a member of a homologous series
What is the structural formula??
The minimal detail that shows the arrangement of atoms in a molecule
What is the displayed formula??
The relative positioning of atoms and the bonds between them
What is the skeletal formula??
The simplified organic formula showing only a carbon skeleton and associated functional groups
Functional group
A group of atoms responsible for the characteristic reactions of a compound
Formula for an alkyl group
CnH2n+1
What does aliphatic mean??
A compound containing carbon and hydrogen
Joined in straight chains, branched chains or non-aromatic rings
What does alicyclic mean??
An aliphatic compound arranged in non-aromatic rings with or without side chains
What does aromatic mean??
A compound containing a benzene ring
What does saturated mean??
Single carbon carbon bonds only
What does unsaturated mean??
The presence of multiple carbon-carbon bonds
What is a structural isomer??
Compounds with the same molecular formula but different structural formula
Why does ionisation energy increase across a period??
Increasing nuclear charge
No change in shielding
Atomic radius decreases
Nuclear attraction increases
More energy needed to remove outer electron
Why does ionisation energy decrease down a group??
Atomic radius increases
More full inner shells so more shielding
These factors outway the increased nuclear charge
Nuclear attraction decreases
Less energy is needed to remove the outer electron
Why do successive ionisation energies increase??
Same nuclear charge
Fewer electrons
Electrons pulled closer to the nucleus
Nuclear attraction increases
More energy needed to remove the next electron
What is atomic orbital??
Area around the nucleus that can hold 2 electrons with opposite spin
What is an orbital??
A region around the nucleus that can hold up to 2 electrons with orbital spin
What is a shell??
Region around the nucleus which contains orbitals with the same principle quantum number
What is a subshell??
A group of orbitals with the same principle quantum number
How to detect carbonate ions are present
Add dilute nitric acid
Indication that carbonate ions are present when dilute nitric acid is added
Effervescence
How to prove gas produced is carbon dioxide??
Bubble gas through limewater which will turn cloudy
How to detect sulphate ions
Add nitric acid and barium nitrate solution
What will occur if sulphate ions are present when nitric acid and barium nitrate solution is added??
A white precipitate of barium sulphate shows the presence of sulphate ions
Equation of the qualitative analysis of carbonate ions
2H+ + CO32- ~~~> CO2 + H20
Equation of the qualitative analysis of sulphate ions
Ba2+ + SO42- ~~~> BaSO4
How to detect for the presence of a halide ion
Add nitric acid and then silver nitrate solution to an aqueous solution of the sample
After adding nitric acid and silver nitrate solution to a sample, what will indicate a halide ion is present
A white, cream or yellow precipitate will mean a halide ion is present
Equation of the qualitative analysis of halide ions
Ag+ + X- ~~~> AgX
How to determine WHICH halide ion is present
Add ammonia
If a Cl- halide ion is present what will be the colour of the precipitate when ammonia is added
White
If a Br- halide ion is present what will be the colour of the precipitate when ammonia is added
Cream
If a I- halide ion is present what will be the colour of the precipitate when ammonia is added
Yellow
What is the solubility of a Cl- ion in NH3
Soluble in dilute NH3
What is the solubility of a Br- ion in NH3
Soluble in concentrated NH3
What is the solubility of an I- ion in NH3
Insoluble in concentrated NH3
Test for carbonates
Add nitric acid
Test for sulphates
Add barium nitrate
Test for halides
Add silver nitrate
Which ion should be tested for first and why??
By testing for carbonate ions first, subsequent tests are only needed if the unknown is not a carbonate
When does the sulphate test not work??
When carbonate ions are present
If carbonate ions are present, a false positive could be produced
Qualitative analysis of ammonium ions
Add sodium hydroxide solution
What happens when sodium hydroxide solution is added to a solution containing ammonium ions??
Ammonia gas is produced
No effervescence as the ions are very soluble
Equation for the qualitative analysis of ammonium ions
NH4+ + OH- ~~~> NH3 + H2O
How to test for ammonia gas
Warm the mixture to release ammonia gas
Test the gas with damp RED litmus, the alkaline gas will turn the litmus BLUE
When is limestone used in the blast furnace??
In the extraction of iron
When limestone is heated what is formed??
CaO (quicklime) and CO2
What happens when limestone is firstly heated then water is added??
Slaked lime is formed
Ca(OH)2
What happens when limestone is heated then excess water is added??
Limewater is formed
Ca(OH)2
What happens when CO2 is added to limewater??
Calcium carbonate is formed
Limewater turns milky because a precipitate is formed
What happens when excess CO2 is added to limewater
Ca(HCO3) is formed
Present in hard water
Why is limestone heated with clay in a kiln
To make cement
When cement is mixed with sand, water and crushed rock what is formed??
Concrete
Why is limestone used in lakes and soils
To neutralise acidity
What is oxidation
Loss of electrons
Gain of oxygen
What is reduction??
Gain of electrons
Loss of electrons
Physical properties of group 2 elements
- High melting and boiling point (higher than group 1 but lower than transition elements)
- atomic radii increases upon descent down a group
- increased shielding outweighs increased nuclei charge
- ionisation energy decreases down the group
Redox reactions of group 2 elements
All group 2 elements react readily with o2, h2o and dilute acids
What is the trend in ionisation energies down group 2
Sum of the 1st and 2nd ionisation energies decrease down the group
Reactions of group 2 elements with oxygen
All burn in oxygen
Reactivity increases down a group
Observation of magnesium reacting with oxygen
Silver solid burns with a bright white light to form a white solid
Equation of magnesium reacting with oxygen
Mg (s) + O2 (s) ~~~> 2MgO (s)
Reaction of group 2 elements with water
Reactivity increases down a group
Reaction of beryllium with water
No reaction
Reaction of magnesium with water
Reacts with steam
Silver solid reacts slowly with effervescence to produce a cloudy solution
Resulting solutions are alkaline
Alkalinity increases down a group as the hydroxide becomes more soluble
Reaction of ca/sr/Ba with water
Reacts with cold water
Group 2 reactions with dilute acids
All react with dilute acids
Reactivity increases down the group
Uses of group 2 compounds
Limestone
Quarried for building materials
Products used to neutralise acidic soil/emissions
Uses of Mg(OH)2 and CaCO3
Antacids
Neutralise excess stomach acid and prevent acid indigestion
Uses of BaSO4
Barium meal
Insoluble so not absorbed into the blood stream
X-rays cannot pass through so enables X-rays of the digestive tract to be taken
Physical properties of the halogens
Low mp and bp (increases down the group due to increasing strength of induced dipole dipole interactions)
Atomic radio increases down the group
Solubility - non polar molecules dissolve well in non polar solvents
Appearance of cl2 at rtp
Pale green gas
Appearance of Br2 at rtp
Orange/brown liquid
Appearance of I2 at rtp
Silver/grey solid
Colour of cl2 in a non polar solvent
Pale green
Colour of br2 in a non polar solvent
Orange
Colour of i2 in a non- polar solvent
Purple/pink
Colour of cl2 in water
Very pale green
Colour of br2 in water
Orange
Colour of i2 in water
Yellow/brown
Oxidising strength in halogens
Decreases down a group
Displacement reactions in halogens
An element higher up in the group will displace an ion lower down from its compound
Reaction of chlorine with water
Chlorine disproportionates
Equation to show the disproportionation of Cl2
Cl2 + H2O ~>~
What is disproportionation
The same element is simultaneously oxidised and reduced
Disproportionation of chlorine with an alkaline
2NaOH + Cl2 ~~~> NaCl + NaOCl + H2O
Conditions of a reaction between chlorine and an alkali
Cold (below room temp)
Using dilute NaOH
Ionic equation EXAMPLE with silver nitrate
X- + Ag+ ~~~> AgX
What is used to distinguish between Cl and Br/I
Use Silver nitrate
Uses of chlorine
Water treatment
Chlorine bleach
Bromine manufacture
Production of Organochlorine compounds such as PVC, solvents and Pesticides
Pros of cl2 in water treatment
Kills bacteria
Prevents spread of disease through water supply
Cons of cl2 in water treatment
Toxic so careful handling required
May react with hydrocarbons in water forming harmful substances
