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Chemistry > Periodicity > Flashcards

Periodicity Flashcards

1
Q

What is periodicity?

A

Repeating patterns seen across different periods

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2
Q

What is first ionisation energy?

A

Energy needed to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

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3
Q

What are the factors affecting value of an element’s ionisation energy?

A
  • Atomic radius
  • Nuclear charge
  • Shielding
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4
Q

What does first ionisation energy show an overall increase across periods?

A
  • Nuclear charge increases as there are more proton as you go across the period
  • Therefore, atomic radius decreases as there is an increase nuclear attraction so the electrons are pulled in more
  • Also, the shielding stays the same
  • These factors mean that it is harder to lose outer shell electron so more energy is required
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5
Q

Why does first ionisation energy decrease down the group?

A
  • Atomic radius increases as there are more energy levels so a greater distance between nucleus and outermost orbital
  • Increased shielding as there are more energy levels
  • Increased nuclear charge as there are more protons
  • However increase shielding and atomic radius are more significant factors so outer shell electrons are easier to lose so less energy is required
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6
Q

What group has the highest first ionisation energy?

A

Group 18

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7
Q

Which element has the highest ionisation energy?

A

Helium

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8
Q

What is second ionisation energy?

A

Energy needed to remove 1 mole of electrons from 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions

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9
Q

How to identify an element from ionisation energy data?

A

Period 3 element

1st- 789
2nd- 1577
3rd- 3232
4th- 4556
5th- 16091

Element is silicon as it must have 4 electrons in outer shell as the ionisation energy increases dramatically from 4th to 5th energy

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10
Q

Why does the melting point increase from group 1 to group 14?

A
  • Group 1 and 13 metals increase as the strength of metallic bond increases as you go across the period, there are more delocalised electrons, which means more electrons are contributed to the metallic bond. Also, more electrons means the ion has a greater effect nuclear charge so more energy is required to overcome the electrostatic attraction
  • Also, group 14 are giant covalent structures and therefore a lot of energy is required to break the strong covalent bonds
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11
Q

Why does the melting point remain relatively constant from 14 to 15?

A

Because group 15 are simple molecular structure and so only contain London Forces, so very little energy is required to overcome the forces

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12
Q

Why does melting point stay consistent from 15 to 18?

A

Because they are simple molecular structure that have London forces which require a lot less energy to overcome

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13
Q

What is slaked lime?

A
  • Calcium hydroxide produced when calcium oxide is mixed with water
  • Used in many applications, such as food preparation, sewage treatment and paper production
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14
Q

What is the chemical name for a barium meal?

A

Barium sulfate

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15
Q

What is a barium meal used for?

A

Used as a radiocontrast agent most commonly used in x ray imaging of the gastrointestinal tract because it is an X ray absorber which appears white on film.

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16
Q

Why can barium be swallowed as a barium meal, even though it is toxic?

A

Because it is insoluble in an aqueous media

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17
Q

State the chemical formula for the main ingredient in Milk of Magnesia?

A

Mg

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18
Q

What is milk of magnesia used for?

A

Used to relieve indigestion and heartburn as it can reduce the amount of stomach acid while increasing water in the intestines.

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19
Q

What is formed when a group 2 metal oxide reacts with water?

A

Metal hydroxide

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20
Q

Write an equation to show the formation of a metal hydroxide from a group 2 metal oxide and water

A

MO(s) + H2O (l) —–> M2+(aq) + 2OH- (aq) which BECOMES M2+ (aq) + 2OH (aq) —> M(OH)2 (s)

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21
Q

What does the reaction of a group 2 metal and steam produce?

A

Group 2 metal oxide

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22
Q

Construct an equation of group 2 metal and steam

A

Mg (s) + H2O (g) —-> MgO (s) +H2 (g)

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23
Q

Name another calcium compound, that is often found in remedies to treat indegestion

A

Calcium carbonate

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24
Q

Explain the the use of Ca(OH)2 in agriculture to neutralise acid soils

A

Ca(OH)2 combines with H+ ions to form neutral water therefore increasing pH of acidic soil. But is widely available and is sparingly soluble in water so acts as a slow release neutraliser

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25
Q

Explain use of Mg(OH)2 in some indigestion tablets as an antacid

A

Mg(OH)2 decrease amount of stomach acid and increases volume of water in small intestine. It combines with H+ ions to form neutral water. But Mg(OH)2 is less alkaline and mild enough to ingest

26
Q

Do halogens gain or lose electrons?

A

Gain electrons to form negative ions

27
Q

How does the configuration of halogens always end?

A

s2p5 (outer shell)

28
Q

What happens to the boiling point of halogens as you go down the group?

A

Increases down the group

29
Q

What happens to the reactivity of halogens as you go down the group?

A

Decreases down the group

30
Q

What happens to the reactivity of group 2 as you go down the group?

A

Increases down the group

31
Q

What happens to the solubility and alkalinity of group 2 as you go down the group?

A

Solubility and alkalinity increases

32
Q

What happens to the boiling point of group 2 as you go down the group?

A

Decrease as you go down the group

33
Q

Why does the reactivity of halogens decrease down the group?

A

-Harder to gain an electron as atomic radius increases, more shells mean more shielding and so less nuclear attraction to capture an electron from another species

34
Q

What is the rule with halides?

A

A more reactive halogen will always replace a less reactive halide

35
Q

What do the halogens look like at RTP?

A
  • Cl2 is a pale green gas
  • Bromine is an orange liquid
  • Iodine is a solid with grey-black crystals
36
Q

What halides does chlorine displace?

A
  • Potassium bromide

- Potassium iodide

37
Q

What halides does bromine displace?

A

Potassium iodide

38
Q

What halides does iodine displace?

A

None

39
Q

What is the test for halide ions?

A
  1. Add a few drops of silver nitrate to sample
  2. Gently shake test tube and observe any precipitate that forms
    Results:
    -White precipitate will form for chloride ions
    -Cream precipitate for bromide ions
    -Yellow precipitate with iodide ions
40
Q

What is the issue with just using silver nitrate for a halide test?

A

These results can be hard to distinguish as the colours are similar

41
Q

What test can you do to confirm the identity of the halide ions?

A

1) Add some dilute ammonia to sample and if white precipitate dissolves then Cl- ions are present
2) Other two remaining solutions, add concentrated ammonia to sample, the sample that dissolves first is Br- ions
3) Remaining solution is I- ions

42
Q

Are silver halides soluble in water?

A

No

43
Q

What is the carbonate test?

A

1) In a test tube, add dilute nitric acid to the solid or solution to be tested
2) If you see bubbles, the unknown compound could be a carbonate
3) Bubble gas through lime water
4) If limewater turns cloudy then carbonate ions are present
CO2 reacts to form a fine white precipitate of calcium carbonate, turning the water cloudy

44
Q

What is the sulfate test?

A

1) Add barium nitrate to unknown compound

2) Barium ions will react with any sulfate ions and form a white precipitate

45
Q

What is the correct sequence for anion tests?

A

1) Carbonate
2) Sulfate
3) Halides

46
Q

Why is there a correct order for the tests? (Carbonate)

A

Carbonate:

  • Neither sulfate nor halide ions produce bubbles with dilute nitric acid
  • Can be carried out without possibility of incorrect test
  • If test produces no bubbles , no carbonate ions are present and you can move on
47
Q

Why is there a correct order for the tests? (Sulfate)

A
  • Barium carbonate is insoluble and also forms a white precipitate
  • If you carry out a sulfate test with carbonate ions remaining you may get a false result
  • So only proceed once there are no carbonate ions left
48
Q

Why is there a correct order for the tests? (Halide)

A
  • Silver carbonate and silver sulfate are both insoluble in water and will form precipitates
  • Therefore it is important to remove both carbonate and sulfate ions from the solution before adding silver nitrate to prevent false results
49
Q

How do you carry out tests if you have a solution with a mixture of ions?

A
  • Carry out tests in same order
  • In carbonate test, add nitric acid until there are no more bubbles then you know you’ve removed all of the carbonate ions
  • To solution left, add an excess of barium nitrate then filter the solution to remove the precipitate of Barium sulfate. Then, you know you have removed all of the sulfate ions.
  • Then add silver nitrate to test for halides, CO3^2-, SO4^2- ions have been removed so precipitate formed must involve halide ions
50
Q

What is the test for cations?

A
  • Add some sodium hydroxide to the solution
  • Ammonia gas is produced however you are unlikely to see gas bubbles
  • Therefore, the mixture is heated so the gas is released
  • Test gas with moist pH indicator paper
  • Ammonia gas is alkaline and therefore will turn the paper blue
  • Ammonia gas can be dangerous so the solution must be heated gently
51
Q

What is disproportination?

A

Oxidation and reduction of the same element in a redox reaction

52
Q

What does the reaction of chlorine with water form?

A

Chloric acid and hydrochloric acid

53
Q

What is the equation for chlorine with water, including oxidation numbers?

A

Cl2(g) + H2O (l) ——> HClO (aq) + HCl (aq)

O. +1. -1

54
Q

What are chloric acid and chloride ions used for?

A

Used to purify drinking water as it can kill bacteria, preventing outbreaks of cholera and typhoid
Chloric acid can also behave as a weak bleach

55
Q

What is the risk with chlorinating water?

A

Chlorine can react with organic matter to form traces of chlorinated hydrocarbons which are suspected of causing cancer

56
Q

What is formed when you react chlorine with sodium hydroxide?

A

Sodium chlorate, sodium chloride and water

57
Q

What is the equation, including oxidation numbers, for the reaction between chlorine and sodium hydroxide

A
  1. +1
    Cl2 (g) + 2NaOH (aq) ——> NaClO (aq) +NaCl + H20
    -1
58
Q

Why is there a drop in FIE between nitrogen and oxygen?

A
  • Because all of nitrogen’s p orbitals contain one electron
  • However, oxygen has one p orbital with paired electrons that repel each other
  • Due to this repulsion, it is easier to remove one of these electrons
59
Q

Why is there a drop in FIE between Be and B?

A
  • Be’s outer shell electron is in the s orbital whereas the outer shell electron in B is lost from the p orbital
  • The p orbital has a higher energy level than the s orbital and therefore the electron is easier to remove
60
Q

What happens to solubility as you go down group 2?

A

Solubility increases

61
Q

What happens to alkalinity as you go down group 2?

A

Alkalinity increases

62
Q

Equation for group 2 metal with water

A

M (s) + H20 (l) —–> M(OH)2 (aq)

Chemistry (11 decks)

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