3.1 The Periodic Table (completed) Flashcards
3.1.1 Periodicity 3.1.2 Group II 3.1.3 Group VII
How is the periodic table arranged?
- Increasing atomic number
- Chemically similar elements
- Occur in the same groups
What is the trend for atomic radius across a period?
Decreases
Number of protons in nucleus increase so nuclear charge increases
The electrons are pulled in with a greater force shortening the atomic radius
What is the trend for first ionisation energy across a period?
Increases
The number of protons increase so there is more attraction acting on electrons
There is the same number of shells so same level of shielding but more nuclear charge
What is the trend for melting points across period three?
Na to Al: increases as there are more electrons in delocalised sea of electrons increasing force of attraction
Si: large increase due to giant molecular structure a lot of energy is required to break the bonds
P to Ar: much lower due to simple covalent molecules and weak intermolecular London forces the larger molecule the greater number of electrins and the stronger the London forces sulphur is larger as it exists as S8
What is the trend for first ionisation energy down a group?
Decreases
Number of shells increase so distance between nucleus and outer electrons decreases with a weaker attraction force and also more shielding electrons
What is group 2?
Alkali earth metals
What is the trend in reactivity down group two?
Increases
Electrons become easier to remove as the outer electrons are further from the inner attracting nucleus
More shielded from the attracting nucleus
Therefore if easier to remove it is easier to react
What is the reaction of group two metals with hydrochloric acid?
Acid + Metal → Salt + Hydrogen
What is the reaction of group two metals with oxygen?
Metal + Oxygen → Metal Oxide
What is the reaction of group two metals with water?
Metal + Water → Metal hydroxide + Hydrogen
How does the solubility of group two hydroxides change down the group?
Increases
More OH- in solution therefore the solution becomes more alkaline
What is the trend of thermal decomposition of group two carbonates?
All undergo thermal decomposition to give the corresponding white metal oxide and CO2
It becomes more difficult to decompose down the group
What is the reaction of group two oxides with water?
Metal oxide + Water → Metal hydroxide
What is calcium hydroxide used for?
It is used by farmers and gardeners to neutralise acid soils
What is magnesium hydroxide used for?
Milk of magnesia
It’s used to relieve indigestion by neutralising excess acid in the stomach
What is barium chloride used for?
Barium sulphate is an insoluble white precipitate so barium chloride can test for sulphate ions
Barium nitrate can also be used for this
What are group seven elements?
Halogens
What are the characteristics of halogens?
They are all diatomic all form ionic salts and all toxic
What is the trend in boiling points down group seven?
Increases
More electrons stronger London forces more energy to break
What is the trend for reactivity down group seven?
Decreases
Closer to the nucleus experiencing less shielding stronger force of attraction
How does the ability to be reduced change down group seven?
Decreases
Gain of electrons
Further from the nucleus experience is more shielding less force of attraction
What are oxidising agents?
Molecules or elements that gain electrons to make ions
e.g. halogens becoming halide ions
What colour are the halogens in aqueous solutions?
Fluorine - pale yellow
Chlorine - pale green
Bromine - orange
Iodine - red/brown
What colour are halides?
Colourless
What are halogen displacement reactions and how can they be used?
They are redox reactions where the most reactive is reduced and the least reactive is oxidised
They can be used to identify which halogens are present in a solution as halide is a colourless but halogens have a specific colour
How do aqueous halogens appear when shaken with cyclohexane?
Halogens are non-polar molecules and will dissolve best and non-polar solvents such as cyclohexane
Cyclohexane will not mix with water so two distinct layers will form
Bromine - orange
Iodine - purple
How can you test for halides?
They form a precipitate with silver nitrate and you can then dissolve them with ammonia
What halogen precipitates are formed with silver nitrate?
F- Clear solution
Cl- White precipitate
Br- Cream precipitate
I- Yellow precipitate
What happens when silver nitrate precipitates have added to dilute ammonia?
Cl- Colourless solution
Br- Cream precipitate
I- Yellow precipitate
What happens when silver nitrate precipitate have added to concentrated ammonia?
Br- Colourless solution
I- Yellow precipitate
What is a disproportionation reaction?
When one element is oxidised and reduced in the same reaction
What is the reaction between chlorine and water and what is it used for?
Cl2 + H2O → HCl + HClO
Killing Bacteria
What is the reaction of chlorine with aqueous sodium hydroxide?
Cl2 + 2NaOH → NaCl + NaClO + H2O
NaClO is sodium hypochlorite
It is a key ingredient in household bleaches
Explain why xenon has a lower first ionisation energy than neon
[3 marks]
Xe has a bigger atomic radius
Xe has more shielding
The nuclear attraction to the outermost electron decreases so less energy is required to remove an electron
Explain the difference in melting point for the elements Na and Mg
[3 marks]
Magnesium ions have a greater charge
Magnesium has more delocalised electrons
Magnesium has greater attraction between ions and
electrons so more energy is required to break metallic bonds
Explain the decrease in the atomic radii across the period from Na to Cl
[3 marks]
nuclear charge increases
shielding remains the same
greater attraction pulls the electrons closer in
