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A Level Chemistry-CIE > Chemical Periodicity > Flashcards

Chemical Periodicity Flashcards

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1
Q

Define periodicity

A

The repeating patterns in physical and chemical properties of elements across the periodic table is called periodicity.

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2
Q

Define atomic radius

A

The atomic radius is the distance between the nucleus and the outermost electron of an atom
The atomic radius is measured by taking two atoms of the same element, measuring the distance between their nuclei and then halving this distance
In metals this is also called the metallic radius and in non-metals, the covalent radius

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3
Q

What is the trend of atomic radius across a period?

A

Across the period, the atomic radii decrease.

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4
Q

Explain the trend of atomic radii across a period.

A
  • The number of protons (the nuclear charge) and the number of electrons increases by one every time you go an element to the right
  • The elements in a period all have the same number of shells (so the shielding effect is the same)
  • This means that as you go across the period the nucleus attracts the electrons more strongly pulling them closer to the nucleus
    Because of this, the atomic radius (and thus the size of the atoms) decreases across the period
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5
Q

What is the periodic pattern of ionic radii?

A

The ionic radii decreases across a period.

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6
Q

What is ionic radius?

A

The ionic radius is the distance between the nucleus and the outermost electron of an ion

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7
Q

What type of ions do non metals produce?

A

non-metals produce negatively charged ions (anions)

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8
Q

What types of ions do metals produce?

A

Metals produce positively charged ions (cations).

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9
Q

What is the trend of ionic radius in period 3 anions?

A

The** anions are larger than their original parent atoms because each atom has gained one or more electrons in their third principal quantum shell
This increases the repulsion between electrons, while the nuclear charge is still the same, causing the electron cloud to spread out
Going across P3- to Cl- the ionic radii decreases **as the nuclear charge increases across the period and fewer electrons are gained by the atoms (P gains 3 electrons, S 2 electrons and Cl 1 electron)

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10
Q

What is the trend of ionic radius in period 3 cations?

A

The** cations** have lost their valence electrons which causes them to be much smaller than their parent atoms
Because there are less electrons, this also means that there is less shielding of the outer electrons
Going across the period from Na+ to Si4+ the ions get smaller due to the increasing nuclear charge attracting the outer electrons in the** second principal quantum shell **nucleus (which has an increasing atomic number)

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11
Q

What is melting points across periods dependent on?

A

The change in melting point across a period reflects the type of structure and bondihng.

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12
Q

What is the periodic trend in melting points for period 3 elements?

A

A general increase in melting point for the Period 3 elements up to silicon is observed. This is because the elements are metals and thus have strong metallic bonding.
Silicon has the highest melting point. This is because silicon has giant covalent structure.
After the Si element, the melting points of the elements decrease significantly as they have simple molecular structures.The covalent bonds within the molecules are strong, however, between the molecules, there are only weak instantaneous dipole-induced dipole forces
It doesn’t take much energy to break these intermolecular forces

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13
Q

Define electrical conductivity.

A

Electrical conductivity refers to how well a substance can conduct electricity

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14
Q

What is the periodic trend in electrical conductivity in group 3 elements?

A

Metals are good conductors of electricity because of their delocalised electrons.
Electrical conductivity increases from sodium to magnesium to aluminium. This is because each atom donates its own respective electrons. Due to the giant molecular structure of Si, there are no delocalised electrons that can freely move around within the structure
Si is therefore not a good electrical conductor and is classified as a semimetal (metalloid).
After the metals the electrical conductivity of the elements decreases.

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15
Q

What is the periodic trend in first ionisation energy in group 3 elements?

A

There is a general increase in first ionistion energy across a period because the increasing nuclear charge and decreasing atomic radius makes the attractive forces between the nucleus and outer electrons greater. remeber that group 13 and group 16 elements may not obey this rule.

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16
Q

Which elements in period 3 react with oxygen?

A

All elements in group 3 react with oxygen to form oxides except chlorine and argon.

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17
Q

Describe the reaction between sodium and oxygen?

A

4Na (s) + O2 (g) → 2Na2O (s)
Vigourous reaction under heat
Sodium burns with a bright yellow flame to produce a white solid.

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17
Q

Describe the reaction between magnesium and oxygen.

A

2Mg (s) + O2 (g) → 2MgO (s)
Vigorous reaction under heat
Magnesium burns with a bright white flame to produce a white solid.

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18
Q

Describe the reaction between aluminium and oxygen.

A

4Al (s) + 3O2 (g) → 2Al2O3 (s)
fast reaction and powdered aluminium.
Aluminium burns with a bright white flame and forms a white powder as a product.

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19
Q

Describe the reaction between silicon and oxygen.

A

Si (s) + O2 (g) → SiO2 (s)
Powdered Si is heated strongly and the reaction is slow,
Silicon burns with bright white sparkles.
The product is a white powder.

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20
Q

Describe the reaction between phosphurus and oxygen.

A

4P(s) + 5O2(g)→P4O10(s)
vigourous reaction under heat
Phosphorous burns with a yellow or white flame
The product is white clouds

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21
Q

Describe the reaction between sulfur and oxygen.

A

S (s) + O2 (g) → SO2 (g)
Gentle reaction in which powdered Sulfur is heated
Sulfur burns with a blue flame
The product is toxic fumes

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22
Q

Which elements from period three react with chlorine?

A

All of them except argon and sulfur(does for chloride but not in syllabus).

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23
Q

Describe the reaction between sodium and chlorine?

A

2Na(s)+Cl2(g)→2NaCl(s)
Sodium is heated and there is a vigourous reaction.

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24
Q

Describe the reaction between magnesium and chlorine.

A

Mg (s) + Cl2 (g) → 2MgCl2 (s)
Magnesium is heated and it is a vigourous reaction

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25
Q

Describe the reaction between aluminium and chlorine.

A

2Al (s) + 3Cl2 (g) → Al2Cl6 (s)
Aluminium is heated and it is a vigorous reaction.

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26
Q

Describe the reaction between silicon and chlorine?

A

Si (s) + 2Cl2 (g) → SiCl4 (l)
Silicon is heated and the reaction is slow.

27
Q

Describe the reaction between phosphorus and chlorine.

A

2P (s) + 5Cl2 (g) → 2PCl5 (l)
Phosphorus is heated and in excess chlorine.
Slow reaction.

28
Q

Give the equation for the reaction of sodium with water.

A

2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

Water should be cold.

29
Q

Explain what happens to sodium when it reacts with water.

A

The sodium melts into a ball and moves across the water surface until it disappears
Hydrogen gas is given off
The solution formed is strongly alkaline (pH 14) due to the sodium hydroxide which is formed

30
Q

What is the reaction between magnesium and water?

A

Mg (s) + 2H2O (l) → Mg(OH)2 (aq) + H2 (g)
The solution formed is weakly alkaline (pH 11) as the formed magnesium hydroxide is only slightly soluble

Water is cold

31
Q

What is the reaction between magnesium and water when magnesium is heated.

A

When magnesium is heated, it reacts vigorously with steam (water) to make magnesium oxide and hydrogen gas:
Mg (s) + H2O (g) → MgO (s) + H2 (g)

32
Q

Describe the oxidation states of period 3 oxides.

A

Oxygen is more electronegative than any of the Period 3 elements
Therefore, the Period 3 elements will have positive oxidation states in their oxides, while the oxygen has a negative oxidation state of -2

33
Q

Describe the oxidation state of period 3 chlorides.

A

Chlorine is more electronegative than the other Period 3 elements
Therefore, the other Period 3 elements will generally have positive oxidation states in their chlorides, while the chlorine has a negative oxidation state of -1.

34
Q

What is an oxidation number?

A

The oxidation number (also known as oxidation state) is a number given to each atom or ion in a compound to keep track of how many electrons they have
In a single ion or molecular ion, the oxidation number tells us how many electrons have been lost or gained
Positive oxidation number = loss of electrons
Negative oxidation number = gain of electrons

35
Q

What is the oxidation number of sodium oxide.

A

Na2O
Oxidation no of sodium=+1

36
Q

What is the oxidation number of magnesium oxide?

A

MgO
Oxidation number of magnesium=+2

37
Q

What is the oxidation number of Aluminium oxide?

A

Al2O3
Oxidation number of aluminium=+3

38
Q

what is the oxidation number of silcon dioxide?

A

SiO2
Oxidation number of silicon=+4

39
Q

What is the oxidation state of phosphorous oxide?

A

P4O10
Oxidation state of phosphorus=+5

40
Q

What is the oxidation number of sulfur oxide?

A

SO2=Oxidation number of sulfur=+4
SO3=Oxidation number of sulfur=+6

41
Q

What is the oxidation number of chlorine oxide?

A

Cl2O7=+4,+6,+7
Cl20=+1
Cl2O3=+5

42
Q

Deducing oxidation numbers of Period 3 elements in their oxides?For example P4O10?

A

P4O10
10 O atoms = 10 x (–2) = –20
The overall charge of the compound = 0
4 P atoms = +20
Oxidation number of 1 Al atom = (+20) / 4 = +5

43
Q

What is the oxidation number of sodium chloride?

A

NaCl=oxidation number of Na=+1

44
Q

What is the oxidation number of magnesium chloride?

A

MgCl2=Oxidation number of magensium=+2

45
Q

What is the oxidation number of Aluminium chloride?

A

AlCl3=Oxidation number of aluminium=+3

46
Q

What is the oxidation number of Silicon tetrachloride?

A

SiCl4=Oxidation number of silicon=+4

47
Q

What is the oxidation number of phosphorus chloride?

A

PCl5=Oxidation number of phosphorus=+5
PCl3=Oxidation number of phosphorus=+3

48
Q

What is the oxidation number of sulfur chloride?

A

SCl2=oxidation state of sulfur=+2
S2Cl2=oxidation state of sulfur=+1

49
Q

What is an amphoteric compound?

A

Compounds that are able to behave as both an acid and as a base are called amphoteric. Aluminum oxide is an amphoteric oxide because it reacts with both acids such as hydrochloric acid and bases such as sodium hydroxide to form salts.

50
Q

Describe the reaction of sodium oxide and water.

A

Na2O(s)+H20(l)→2NaOH(aq)
it is a strongly alkaline soulution (12-14)

51
Q

what is the reaction between magnesium oxide and water?

A

MgO (s) + H2O (l) → Mg(OH)2 (aq)
weakly alkaline solution e.g. pH 10

52
Q

describe the reaction between aluminium oxide and water.

A

Aluminium oxide does not react with water or dissolve in water, which is why an oxide layer can protect aluminium metal from corrosion. However it does react and dissolve when added to acidid or alkaline solutions.

53
Q

Describe the reaction between alumium oxide with acid.

A

Al2O3+3H2SO4→Al(SO4)3 +3(H2O)(l)
When aluminium oxide reacts with an acid it behaves as a base:It forms a salt (alumium sulfate) plus water.

54
Q

Describe the reaction between aluminium oxide and hot concentrated alkali:

A

Al2O3(s)+2NaOH(aq)+3H20(l)→2NaAl(OH)4(aq)
When alumium oxide reacts with an alkali it behaves as an acid:reacting to form a salt (sodium teterahydroxoaluminate).

55
Q

Describe the reaction between silicon dioxide and water.

A

Silicon dioxide is insoluble in water. Water cannot break its giant molecular structure. However it will react with and dissolve in hot concentrated alkali:
SiO2(s)+2NaOH(aq)→Na2SiO3(aq)+H2O(l).
Silicon dioxide acts as an acid when it reacts with sodium hydroxide, forming a salt (sodium silicate) plus water. It does not react with acids, so it is classed as an acidic oxide.

56
Q

Describe the reaction between phosphorus(v)oxide and water?

A

Phosphorus(v)oxide reacts vigorously and dissolves in water to form a weak acidic solution (3-4) of phosphoric acid (pH2)
p4O10(s)+6H20→4H3PO4(aq) (phosphoric (v) acid)

57
Q

Describe the reaction between the oxides of sulfur and water.

A

The oxides of sulfur, SO2 and SO3, both react and dissolve in water, forming strong acidic solutions (pH1).
SO2(g)+H2O(l)→H2SO3(aq)
sulfurous acid also known sulfuric (IV) acid)
SO3(g)+H20(l)→H2SO4(aq)
Sulfuric (VI) acid.

58
Q

Give one use of magnesium oxide.

A

The high melting points of the giant covalent structure of magnesium oxide is used to line the inside of furnaces.

59
Q

Give one use of aluminum oxide and Silicon dioxide

A

The high melting points of the giant covalent structure of aluminum oxide and Silicon dioxide are used to make ceramics because their structures were designed to withstand high temperatures and provide electrical insulation.

60
Q

What type of solutions do the oxides of sodium and magnesium produce? (B/W acid or base)

A

The oxides of the metals sodium and magnesium with purely ionic bonding produced alkaline solutions with water as there oxide ions. O2-(aq) become hydroxide ions, OH-(aq). The oxide ions behave as bases accepting H+ ions from water molecules:
O2- (aq) + H2O(l)=2OH-(aq)

61
Q

What type of solutions do covalently bonded non metal oxides of phosphorus and Sulfur dissolve and react in water to form?

A

By contrast, the covalently bonded non metal oxides of phosphorus and Sulfur dissolve and react in water to form acidic solutions. The acidic molecules formed donate H+ ions to water molecules, behaving as typical acids. For example sulfuric (VI) acid:
H2SO4(aq)+H2O=H3O+(aq) + HSO4(aq).

62
Q

Does silicon oxide have an acidic or alkaline nature?

A

The insoluble oxide of aluminum shows its acidic nature by reacting and dissolving in an alkaline solution, such as hot concentrated sodium hydroxide solution forming a soluble salt. This behavior is typical of covalently bonded oxide.

63
Q

Describe the pH of the solution formed when period 3 chlorides react with water.

A

NaCl=7
MgCl2=6.5
Al2Cl6=3
SiCl4=2
PCl5=2
SCl2=2

64
Q

Describe a litmus test.

A
65
Q

What is the primary chemical component of sand?

A

Silica SiO2

66
Q

What is effervescence?

A

Some chemical reactions result in a product that is in a different state to the reactants. An example of this is effervescence in which a reaction in a liquid produces bubbles of gas. Effervescence is an indicator of a chemical reaction taking place.

A Level Chemistry-CIE (13 decks)

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