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Chemistry As > Unit 2- Periodic table group 2 and 7 > Flashcards

Unit 2- Periodic table group 2 and 7 Flashcards

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1
Q

Recall the trend in ionisation energies for group 2

2.7.1.a

A
  • Ionisation energy decreases down group 2
  • More electrons as you go down group 2
  • However the attraction between the nucleus and the electrons decrease due to a greater distance and more shielding
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2
Q

Recall the reaction for the group 2 atoms with oxygen

2.7.1.b

A
  • Burns in oxygen
  • Forms ionic oxide
  • Has a general formula of MO where M is a group 2 atom
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3
Q

Recall the reaction of group 2 atom with water

2.7.1.b

A
  • Group 2 atoms react with water
  • Mg reacts slowly in cold water but rapidly with steam on heating
  • Mg + H2O –> MgO + H2
  • Calcium reacts with cold water to produce hydrogen calcium oxide (white precipitate)
  • Ca + H2O –> CaO + H2
  • Barium in water also
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4
Q

Recall the reaction for group 2 elements with chlorine

2.7.1.b

A
  • All group 2 react with chlorine
  • Forms white chlorides
  • General formula of MCl2 where M is a group 2 element
  • Mg + Cl2 –> MgCl2
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5
Q

Recall the reactions with group 2 oxides and water

2.7.1.c

A
  • Reacts with water
  • slightly soluble
  • forms the hydroxide M(OH)2 where M is a group 2 element
  • Calcium oxide reacts vigorously with water
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6
Q

Recall the reaction between group 2 oxides with acids

2.7.1.c

A
  • Reacts with acids to form salts
  • e.g. CaO + 2NHO3 –> Ca(NO3)2
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7
Q

Recall the reaction between group 2 hydroxides and dilute acid

2.7.1.c

A
  • Reacts with acids
  • forms the group 2 element ion and water
  • e.g. Mg(OH)2 + 2H+ –> Mg2+ + H2O
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8
Q

Recall the trend in solubility of group 2 hydroxides and sulfates

2.7.1.d

A
  • Hydroxides solubility increases down group 2
  • Sulfates solbulity decreases down group 2
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9
Q

Recall the trends in thermal stability for group 1 and 2 nitrates and carbonates

2.7.1.e

A
  • thermal stability increases down the group for group 1 and 2
  • group 1 more stable in comparison to group 2
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10
Q

Why are group 1 and 2 more thermically stable going down the group?

2.7.1.e

A
  • Depend on the polarising power of the cation
  • The greater the charge and smaller the ion, the greater the polarising power
  • The more polarising, the less stable
  • Therefore group 1 is more stable in comparison to group 2 due to haveing a +1 charge compared to +2
  • Increases down the group as the molecules get larger therefore less polarising
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11
Q

What do nitrates for group 1 and 2 produce when decomposed?

A
  • Group 1 produces a metal nitrite and oxygen
  • 2NaNO3 –> 2NaNO2 + O2
  • Group 2 produces nitrogen dioxide, oxygen and a metal oxide which includes lithium
  • Mg(NO3)2–> 2NO2 + 0.5O2 + MgO
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12
Q

what do group 2 carbonates decompose into?

A
  • Forms a metal oxide and carbon dioxide
  • CaCO3 –> CaO + CO2
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13
Q

What are the metals and their corrosponding colour? 2.7.1.f

A
  • Potassium-lilac
  • Strontium-carmine/bright red
  • Lithium- Crimson red
  • Sodium- Yellow
  • Barium- Apple/pale green
  • Calcium- Brick red
  • Magnesium-No colour
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14
Q

How are the flame colours produced for the group 1 and 2 elements?

A
  • Upon heating, the electrons become excited
  • When they go back to their normal state, the electrons emit a characteristic wavelength
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15
Q

Explain the characteristics of the halogen atoms

2.7.2.a

A
  • Low boiling and melting temperature
  • Solubility decreases down the group
  • More soluble in hydrocarbons than water
  • Fluorine is a yellow gas
  • chlorine is a green gas
  • Bromine is a red liquid
  • Iodine is a black solid
  • Oxiding power decreases down the group therefore less reactive down the group
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16
Q

Why does the oxiding power of the halogens decrease down the group

2.7.2.a

A
  • As you go down group 7, the elements get larger
  • More screening
  • Therefore a greater electron affinity
17
Q

How does the reducing power change of a halide as you decrease down group 7?

A
  • Increases
18
Q

How to test for halides?

A
  • Add nitric acid to acidify the solution
  • Added to remove impurities
  • Add silver nitrate
  • Silver halide precipitates form
  • Add ammonia for a further test and reaction
19
Q

What are the results when silver nitrate is added to the halogens?

A
  • Fluorine - no reaction
  • Chloride- white
  • Bromide- pale cream
  • Iodide- pale yellow
20
Q

What are the results when ammonia is added to the silver halide precipitates?

A
  • No precipitate for fluorine as soluble
  • AgCl- dissolves to form a colourless solution
  • AgBr- Dissolves only with concentrated ammonia to form a colourless solution
  • AgI- Insoluble in any concentration
21
Q

How do hydrogen halides react with in water?

A
  • Fully ionises
  • e.g. HCl + H2O -> Cl- + H3O+
22
Q

How do hydrogen halides react in ammonia?

A
  • produces a white smoke of an ammonium salt
  • e.g. HCl + NH3 -> NH4Cl
23
Q

What is the reaction for chlorine with cold sodium hydroxide?

A
  • 2NaOH + Cl2 –> NaCl + NaClO + H2O
  • NaClO is sodium chlorate
24
Q

What is the reaction between Chlorine and hot sodium hydroxide?

A
  • 6NaOH + 3Cl2 –> 5NaCl + NaClO3 + 3H2O
  • NaClO3 is sodium chlorate (V)
25
Q

What is the reaction between Iron and halogens?

A
  • Cold fluorine with cold iron wool to oxidise iron into Iron(III) fluoride
  • Chlorine gas passed over hot iron to form iron(III) chloride
  • Bromine vapour passed over hot iron to form Iron(III) bromide
  • Iron is oxidised from an oxidation number of 0 to +3
  • Iodine vapour and hot iron react to form iron(II) iodide
26
Q

What are the reactions for Iron (II) with halogens?

A
  • Bromine and chloride oxidise iron(II) to iron(III)
  • Iodine cannot
  • Iron (II) oxidises iodine into iodide
  • Iron (II) is green while Iron (III) is pale green
27
Q

What is the reaction for halogens with concentrated sulfuric acid?

A
  • Must be added to a solid sample
  • F- forms steamy acid fumes of HF
  • Cl- forms steamy acid fumes of HCl
  • Br- forms steamy acid fumes of HBr which is contaminated with brown bromine vapour
  • I- forms some steamy fumes of HI but mostly purple iodine vapour

Chemistry As (16 decks)

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