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AS LEVEL - CHEMISTRY > 1.6 - The Periodic Table > Flashcards

1.6 - The Periodic Table Flashcards

- Periodic Table Trends, Group 1,2 and 7 chemistry

1
Q

What is the term for rows in the periodic table?

A

Periods

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2
Q

What is the term for columns in the periodic table?

A

Groups

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3
Q

What trend is observed across a period?

A

Ionisation energy

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4
Q

What trends are observed down a group?

A

Physical properties
Same outer electron configuration

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5
Q

What is first ionisation energy?

A

The first ionisation energy of an element is the energy required to remove one electron from each atom in a mole of gaseous atoms.

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6
Q

Which group are the best reducing agents?
Trend in reducing ability in this group?

A

Group 1 - Group 1 elements have better reducing ability down the group
Caesium = most electropositive

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7
Q

What Group is the best oxidising agent?
What is the trend in oxidising ability in this group?

A

Group 7 - Group 7 elements are better reducing agents further up the group.

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8
Q

What is unique about d-Block elements?

A

They often exist in more than one oxidation state, so can both donate and accept electrons

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9
Q

Define Electronegativity

A

The measure of an atom’s ability to attract a bonding electron in a covalent bond.

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10
Q

What is the most electronegative element and what is it given on the Pauling Scale?

A

Fluorine - 4.0

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11
Q

Are elements more or less electronegative across a period - Why?

A

Elements are more electronegative across a period -
- There is an increase in nuclear charge across the period.
- However, bonding electrons are always shielded by the same inner electrons.
- So nuclear charge increases but shielding effect and distance from the nuclear doesn’t.
- This creates greater attraction between the nucleus and the bonding pair.
-This means the element is more able to attract a bonding electron and therefore is more electronegative.

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12
Q

Are elements more or less electronegative down a Group?

A

Elements become less electronegative down a group -
- There is an increase in shielding effect from inner electrons and distance from the nucleus.
-This outweighs the increase in nuclear charge, therefore attraction between the bonding electrons and the nucleus decreases.
- This means the element is less able to attract a bonding electron, therefore it is less electronegative.

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13
Q

What three factors are there when considering the electronegativity of an element?

A

-Nuclear charge
-Distance between the bond and nucleus
-Shielding effect caused by inner electrons

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14
Q

Does first ionisation energy increase or decrease across a period?

A

Generally it increases -
- Increase in nuclear charge
- Electrons are being added to the same shell/ energy level
-Therefore little increased shielding effect
-Therefore, a greater attraction between the nucleus and outer electrons
- Atoms become smaller

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15
Q

Anomalies in first ionisation energy?

A

Groups 2-3
Groups 5-6

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16
Q

Why is there anomaly in F.I.E trends between Group 2-3?

A

There is a decrease in I.E between Groups 2 and 3.
- In Group 3 the outer electron is in a new subshell of a slightly higher energy level.
-The inner s-subshell shields the outer electron reducing the I.E required.

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17
Q

Why is there an anomaly in F.I.E between Groups 5-6?

A

There is a decrease in F.I.E between Group 5-6.
- In Group 5 all of the outer electronsa re in their own orbitals.
In Group 6, the additional electrons shares an orbital.
-The repulsion between electrons in the same orbital makes it easier to remove, therefore a decrease in I.E

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18
Q

Why does ionisation energy decrease down a group?

A

The increase distance from the nucleus + increase shielding effect from inner electrons outweighs the increase in nuclear charge, therefore easier to remove, therefore lower I.E.

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19
Q

What factors does melting point depend on?

A

Structure and bonding present

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20
Q

Melting point trend in Group 1?

A

melting point decreases down the group -
Metallic bonding becomes weaker
-Metallic bonding depends on the attraction of the nucleus to the delocalised valence electrons.
-This becomes weaker upon descending Group 1 as the atoms become bigger and so the valence electrons become further away from the nucleus.

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21
Q

Bonding Trends Across Period 3?
Na, Mg, Al, Si, P, S, Cl, Ar

A
  • Na, Mg and Al - Metallic bonding present therefore high melting point
    Melting point increases in the metals as there is a stronger metallic bonds
    Greater charge and more delocalised electrons per atom.
  • Silicon is a giant covalent structure, therefore very high melting point.
    -P, S and Cl are all simple covalent structures. Weak intermolecular Van der Waals forces result in a low melting point.

-Argon is atomic therefore it is held together by very weak dipole-induced dipole-induced forces, hence the lowest emlting point.

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22
Q

Reactivity in Group 1 and 2 -

A

Reactivity increases down both groups
Atoms get bigger therefore the distance from nucleus increases.
The increase in distance + increased shielding effect from inner electrons outweighs the increase in nuclear charge.
Therefore it easier to form the cation, less energy required.

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23
Q

Difference in reactivity between Group 1 and 2

A

Group 2 is less reactive.
It takes more energy to remove two electrons
Group 2 elements are smaller, therefore increased attraction.

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24
Q

How do you test for cations?

A

Flame test

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25
Q

What do use to perform a flame test?

A

Nichrome Wire - Dipped in HCl

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26
Q

Mg 2+ Flame Colour

A

Colourless

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27
Q

Ca 2+ Flame Colour

A

Brick Red

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28
Q

Sr 2+ Flame Colour

A

Crimson

29
Q

Ba 2+ Flame Colour

A

Apple Green

30
Q

Li + Flame Colour

A

Scarlet

31
Q

Na + Flame Colour

A

Orange/Yellow

32
Q

K+ Flame Colour

A

Lilac

33
Q

Thermal Stability of Group 2 Carbonates and hydroxides

A

Thermal stability increases down the group

34
Q

Products of Group 2 thermal decomposition

A

A metal oxide and a gas

35
Q

Why does thermal stability increase down Group 2?

A

Mg2+ ion is smaller and so has a high charge density. The high charge density polarises the carbonate ion, destabilising it.
This allows it to break down easily
Ba2+ ion has the same charge but is a much larger ion, for this reason it has a low charge density.
The low charge density means it isn’t capable of polarising and by extension destabilising the carbonate ion.
Therefore more heat energy is required for decomposition.

36
Q

Testing rate of thermal decomposition with Group 2 carbonates?

A

CO2 is produced, so limewater can be used to test for the presence of the product CO2.

37
Q

Group 2 reacting with HCl

Group 1 with HCl

A

Sr + 2HCl —-> SrCl2 + H2

Chloride and hydrogen gas
Group 1 is too reactive to be added to acids

38
Q

Group 1 solubility in water?

A

All Group 1 compounds are soluble in water

39
Q

Which Group 2 compounds are always soluble?

A

Nitrates (NO3 -)

40
Q

Which Group 2 compounds are always insoluble?

A

Carbonates (CO3 2-)

41
Q

Trend in Group 2 Sulphates solubility in water

A

Magnesium Sulphate is completely soluble
Ca and Sr are partially soluble - Slight PPT
Barium Sulphate produces a heavy white PPT

42
Q

What type of precipitate can be associated with barium sulphate

A

Heavy/dense white precipitate

43
Q

Trend of Group 2 hydroxide’s solubility in water

A

Less soluble down the Group
MgSO4 is insoluble - White PPT
Calcium and Strontium are partially soluble - Slight white PPT
Barium Hydroxide is soluble

44
Q

How does each Group 1 metal react in water?

A

Li - Fizzes and floats
Na - Forms a ball that fizzes and floats rigorously
K - Ignites and floats

45
Q

Equation for Group 1 metals reacting with water

A

Metal Hydroxide and hydrogen

2Na (s) + 2H20 (l) —-> 2NaOH (aq) + H2 (g)

46
Q

How do Group 2 metals react with water

A

Less vigorously than Group 1
Mg - Requires steam to react

Ca - Bubbles and clouds as a PPT forms
Ba - Greater reaction and clearer solution

47
Q

Equation for Group 2 reacting with water

A

Hydroxide and hydrogen

Ca + 2H2O —-> Ca(OH)2 + H2

48
Q

How do Group 2 metals react with oxygen?

A

Form metal oxides

49
Q

Are metal oxides and hydroxides basic or acidic?

A

Basic

50
Q

Wh

A
51
Q

How do the halogens exist?

A

As diatomic molecules

52
Q

Group 1 and 2 pH in solution

A

Group 1 oxides dissolve to soluble hydroxides as the only product - High pH solution
Group 2 oxides are similar but are less soluble further up the group
So the resulting solution may not have a high pH as the basic hydroxide is solid (PPTed)
Mg(OH)2 solution = Not high pH

53
Q

Melting and boiling point trend in Group 7?

A

Melting point increases down the Group 7 -
- Down the Group the number of electrons increases, this increases the strength of intermolecular Van der Waals forces
Therefore melting point increase

54
Q

Group 7 elements as oxidising agents?

A
  • Down the group atomic radius increases
  • Distance from the nucleus and increase shielding effect.
  • This reduces the effect nuclear charge, therefore more difficult to gain and electrons
  • Therefore, decreased oxidising power.
55
Q

Reaction between Sodium and chlorine?

A

Sodium is burnt in a jar of chlorine gas to form NaCl - It’s a very exothermic reaction

56
Q

Define Volatility

A

How readily a substance vaporises

57
Q

What colour is aqueous Chlorine?

A

Green

58
Q

What colour is aqueous Bromine?

A

Orange

59
Q

What colour is aqueous Iodine?

A

Brown

60
Q

What colour are aqueous halide ions?

A

Colourless

61
Q

Trend of displacement in the Halogens?

A

A halogen can displace halide ions lower down the group.
Chlorine displaces Bromide and iodide
Bromine displaces Iodide

62
Q

What can transition metals be used to show about the halogens and how?

A

Their relative oxidising power
Fluorine reacts with iron and oxidises it from 0 to 3+
In the same reaction iodine oxidises iron from 0 to 2+
Fluorine is therefore the greater oxidising agent

63
Q

How do you test for halides?

A

Silver Nitrate Test

64
Q

What colour precipitates form from silver halides?

A

AgCl - White PPT
AgBr - Cream PPT
AgI - Yellow PPT

65
Q

How do you further test the silver halide precipitate?

A

Add aqueous ammonia

66
Q

How do silver halides react with ammonia?

A

AgCl dissolves in dilute NH3
AgBr dissolves in concentrated NH3
AgI does not dissolve in either concentrated nor dilute NH3

67
Q

Aqueous Cl2 reacts with aqueous Bromide - What colour can be expected at the end of the reaction and why?

A

Orange - The chlorine displaces the Bromide and becomes colourless
Bromide becomes bromine and is orange in colour

68
Q

Pros and cons of using Chlorine to treat water

A

PROS -
- ClO- ion kills bacteria
- Kills bacteria and waterborne diseases (Cholera and Typhoid)

CONS -
- Chlorine can react to form halogenoalkanes which are toxic and carcinogenic.
- Mass medication

69
Q

Pros and cons of using Fluorine to treat water

A

PROS -
- Reduces tooth decay

CONS -
- Can cause fluorosis which damages the enamel
- Mass Medication

AS LEVEL - CHEMISTRY (6 decks)

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