AS Inorganic Chemistry ✅ Flashcards
(40 cards)
How is the periodic table arranged?
- by atomic number (proton number)
- periods (across/rows) = same number of electron shells
- groups (down/columns) = same number of electrons in their outer shells
How can the periodic table be used to work out electronic configuration?
Sally died painfully = SDP
Why does atomic radius decrease across a period?
- as the number of protons increases across the period the electrostatic attraction between the nucleus and outer shell electrons increases reducing the atomic radius
What how does melting point change across a period 3 for the first three metals?
- mp and be increases across the period because the metal-metal bonds get stronger
What is the melting point like from silicon?
- macromolecular with a tetrahedral structure = strong covalent bonds link all its atoms together so it has a high melting point
What is the trend in melting point across period 3 for P, S and Cl?
- all molecular substances
- their melting points depend on their van der waals
- sulphur has the most van der walls so has a higher melting point than p and cl
Why is argon’s melting point so low?
- it exists as individual atoms resulting in very weak van der waal forces
What is the trend ionisation energy across a period?
- increases across a period, due to the increasing attraction between the outer shell electrons and the nucleus due to the number of protons increasing
What is the trend in atomic radius down group 2?
Atomic radius increases down the group = as electron shells are added increasing the shielding and reducing strength of the electrostatic attraction between
What is the trend in first ionisation energy down group 2?
- each element down a group has an extra electron shell compared to the one above
- extra inner shells shield the outer electrons from the attraction of the nucleus
- making it easier to remove outer electrons
What is the trend in reactivity down group 2?
Reactivity increases down the group as group 2 elements lose 2 electrons forming positive ions. It is easier to lose electrons the more reactive the element
What is the trend in melting points down group 2?
Decreases down the group as more shielding means electrostatic attraction is weaker and it is easier to break the bonds
- magnesium is much lower because of its crystal structure
What happens when group 2 elements react with water?
When group 2 elements react they are oxidised from a state of 0 to +2
- group 2 metals react with water to from metal hydroxides and hydrogen
- they react more readily down the group because ionisation energies decrease
How does solubility in group 2 depend on the compound anion?
Group 2 elements that contain singly charged negative ions (e.g. OH-) increase in solubility down the group
Group 2 elements that contain doubly charged negative ions (e.g. SO42-) decrease in solubility down the group
Barium sulphate is said to be insoluble
What is the test for sulphate ions?
- add acidified barium chloride to a solution containing sulphate ions
- if a white precipitate is formed there are sulphate ions present
How are group 2 compounds used to neutralise acidity?
- calcium hydroxide (slaked lime) is used in agriculture to neutralise acid soils
- magnesium hydroxide is used in some indigestion tablets as an antacid
What is barium sulphate used in barium metals for?
- barium sulphate is opaque to x-rays = they wont pass through it but will pass through soft tissues
- a patient swallows the barium meal, barium sulphate coats the tissues making them show up on x-rays
Why is magnesium used in the extraction of titanium?
The main titanium ore, titanium(IV) oxide is first converted to titanium(IV) chloride by heating it with carbon in a steam of chlorine gas
Then the titanium chloride is purified by fractional distillation, before being reduced by magnesium in a furnace at 1000’C
How is calcium oxide and calcium carbonate used to remove sulphur dioxide?
Acidic sulphur dioxide can be removed from flue gases by reacting with an alkali = wet scrubbing
Powered calcium oxide and calcium carbonate can be used
A slurry is made by mixing the calcium oxide or calcium carbonate with water, which is then sprayed onto the flue gases, producing a solid waste product of calcium sulphite
What are the properties of the first 4 halogens?
F2 = gas and pale yellow
Cl2 = gas and green
Br2 = liquid and red-brown
I2 = solid and grey
Their boiling points increase down the group = increasing strength of van der waals forces as the size and mr increases
Electronegativity decreases down the group = increased shielding
Why do halogens displace less reactive halide ions from solution?
A halogen will displace a halide from solution if the halide is below it in the periodic table
- when the halogens react they gain an electron, they get less reactive down the group, less oxidising
- Br will displace Cl, I will displace Br and Cl
How do chlorine and sodium hydroxide make bleach?
Mix chlorine gas with cold, dilute, aqueous sodium hydroxide you get sodium chlorate(I) solution = bleach
2NaOH(aq) + Cl2(g) —> NaClO(aq) + NaCl(aq) + H2O(I)
How does chlorine kill bacteria in water?
Chlorine + water = disproportionation, end up with a mixture of chloride ions and chlorate(I) ions
Cl2(g) + H2O <=> 2H+(aq) + Cl-(aq) + ClO-(aq)
In sunlight = chlorine can decompose water to from chloride ions and oxygen
2Cl2(g) + 2H2O <=> 4H+(aq) + 4Cl-(aq) + O2(g)
Chlorate ions kill bacteria, so adding chlorine to water can make it safe to drink or swim in
What are benefits and drawbacks of using chlorine to treat water?
Pros:
- kills disease-causing microorganisms
- prevents reinfection
- prevents the growth of algae, bad toasters and smells
Cons:
- very harmful to respiratory system when inhaled
- liquid chlorine can cause chemical burns
