The periodic table

What is periodicity?

the repeating pattern of chemical and physical properties of the elements

What does each period represent?

a new energy level

What elements are in the s-block of the periodic table?

groups 1 and 2

What elements are in the p block of the periodic table?

groups 3 to 0

What elements are in the d block of the periodic table?

transition metals

What elements are in the f block of the periodic table?

radioactive elements

What happens to the atomic radius as we move along a period?

It decreases

Why does atomic radius decrease across a period?

Number of protons in an atom increases while the electron shielding remains the same, resulting in greater nuclear attraction between the protons and electrons

What happens to atomic radius moving down a group?

it increases

Why does atomic radius increase down a group?

increasing number of energy levels

Define first ionisation energy

The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

What is the general trend in ionisation energy across a period?

increases

Why does ionisation energy generally increase across a period?

Increased nuclear charge and decreased atomic radius

What is the exception to the trend in ionisation energy in period 3?

Aluminium as it has an electron in a higher energy level than magnesium, making it easier to remove

What are metalloids?

elements that have some properties like metals and some like nonmetals

Going across period 3, what is the general trend in melting and boiling points?

Increases then decreases

Why does the melting and boiling points increase from Na to Al?

metallic bonds become stronger

Why does the trend in melting and boiling points in period 3 peak at silicon?

Silicon has giant covalent structure - strong bonds

Why do melting and boiling points decrease from P to Ar?

Rely on vdw forces

Why does sulfur have a higher melting point than phosphorus?

it is the bigger molecule (S8) - more vdw forces

Why does argon have a very low melting point?

It exists as individual atoms (monatomic) resulting in very weak van der Waals forces

What are elements in Group 2 referred to as?

alkaline earth metals

Are group 2 metals reactive or unreactive?

reactive

What block are group 2 metals in the periodic table?

the s block

What agents do group 2 metals act as?

reducing agents

Why does the reactivity increase going down Group 2?

First ionisation energy decreases as there is more electron shielding

What does reacting a group 2 metal with water produce?

metal hydroxide and hydrogen

What happens to the Group 2 metal's oxidation number when reacted with water?

Goes from 0 to +2

How does the reactivity with water change going down Group 2?

Rate of reaction increases

What happens to the solubility of the Group 2 hydroxides going down Group 2?

It increases - less precipitate forms

What does the concentration of hydroxide ions determine?

The alkalinity of the solution

Which one has the higher pH, magnesium hydroxide or barium hydroxide?

Barium hydroxide as it has a higher concentration of hydroxide ions

What is calcium hydroxide (slaked lime) used for?

neutralising acidic soils

What is magnesium hydroxide (milk of magnesia) used for?

neutralises stomach acid

What happens to the solubility of Group 2 sulphates going down the group?

it decreases

Which group 2 sulfate is insoluble in water?

barium sulfate

What is barium sulfate used for?

Barium meal for X Ray's - lines the digestive tract so it shows up on x ray

How is barium chloride used to test for sulfate ions?

If barium chloride solution mixed with solution containing sulfate ions, barium sulfate is formed which is insoluble - forms white precipitate.

What has to be added to the barium chloride solution before testing for sulfates?

Either hydrochloric acid or nitric acid to react with any carbonate atoms preventing a false positive

What happens to melting and boiling point going down group 7?

It increases - increased vdw forces due to more electrons

What happens to electronegativity going down Group 7?

It decreases - higher atomic radius and more electron shielding reduces nuclear attraction

What does a group 7 halogen act as in a redox reaction?

Acts as an oxidising agent - removes an electron

What happens to reactivity going down group 7?

it decreases - higher atomic radius and shielding means less nuclear attraction - harder to attract an electron

Which element in group 7 is the most powerful oxidising agent?

Fluorine

What happens to oxidising ability going down group 7?

decreases

What happens in a displacement reaction?

A more reactive metal displaces a less reactive metal from a compound

What is produced in a displacement reaction?

A halogen

What is one of the uses of chlorine?

Killing bacteria in water

What is the reaction between chlorine and water?

Cl2 + H2O -> HClO + HCl

What is a disproportionation reaction?

A redox reaction in which the same element is both oxidised and reduced

What are the risks of using chlorine in drinking water?

- Chlorine is a toxic gas

- Chlorine could react with hydrocarbons and create a carcinogen

Describe appearance of fluorine

Yellow gas

Describe appearance of chlorine

Green gas

Describe appearance of bromine

Red-brown liquid

Describe appearance of iodine

Dark grey solid

What do halide ions act as?

reducing agents - donate their electrons to other species

What happens to power of reducing agents going down Group 7?

Increases

Why is fluorine a weak reducing agent?

Small atomic radius and small amount of shielding means strong attraction of outer electrons to nucleus - harder to lose electron

What products are formed when solid sodium chloride reacts with sulfuric acid?

Sodium hydrogensulfate and hydrogen chloride

Why is sulfur not reduced in a reaction between sodium chloride and sulfuric acid?

Chlorine is a weak reducing agent

What is the reaction of sodium bromide with concentrated sulfuric acid?

NaBr(s) + H2SO4(l) → NaHSO4(s) + HBr(g)

2HBr + H2SO4(l) → SO2(g) + 2H2O(l) + Br2(l)

What type of reaction is the reaction of sodium bromide with concentrated sulfuric acid?

A redox reaction as the sulfur is reduced from +6 to +4

What is the reaction of sodium iodide with concentrated sulfuric acid?

NaI(s) + H2SO4(l) → NaHSO4(s) + HI(g)

2HI + H2SO4(l) → SO2(g) + 2H2O(l) + I2(s)

8HI + H2SO4(l) → H2S(g) + 4H2O(l) + 4I2(s)

What can iodine reduce sulfur to in a reaction with sulfuric acid?

- +6 to +4 - SO2

- +6 TO 0 - S8

- +6 TO -2 - H2S

What is used to test for halide ions?

Acidified silver nitrate (AgNO3)

What happens when a silver halide reacts with water?

It forms a precipitate as it is insoluble in water

What colour precipitate is produced when silver nitrate reacts with a chloride ion?

White

What colour precipitate is produced when silver nitrate reacts with a bromide ion?

cream

What colour precipitate is produced when silver nitrate reacts with a iodide ion?

pale yellow

What will silver chloride precipitate dissolve in?

dilute aqueous ammonia

What will silver bromide precipitate dissolve in?

concentrated aqueous ammonia

What will silver iodide precipitate dissolve in?

neither concentrated or dilute aqueous ammonia

Why is dilute nitric acid used in the test for halide ions using silver nitrate solution?

to remove any carbonates or hydroxides

What is produced when chlorine reacts with cold, dilute, aqueous NaOH?

sodium hypochlorate

What is sodium hypochlorite used for?

bleach