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IB Chemistry > Structure 2.1/2 The Ionic and Covalent Model > Flashcards

Structure 2.1/2 The Ionic and Covalent Model Flashcards

1
Q

What are ions?

A

Atoms or groups of atoms with an overall charge

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2
Q

How are ions formed?

A

Transfer of electrons from one atom to another, which results in both atoms having a full outer shell

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3
Q

What do metal atoms generally form in terms of ions?

A

Cations: positively charged ion

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4
Q

What do non-metal atoms generally form in terms of ions?

A

Anion: negatively charged ion

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5
Q

What are ionic compounds?

A

Compounds made up of a combination of cations and anions

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6
Q

What is ionic bonding?

A

Electrostatic attraction between ions of opposite charges

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7
Q

What are transition elements?

A

Elements whose atoms have incomplete d-subshells or who can give rise to cations with incomplete d subshells

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8
Q

What does isoelectronic mean?

A

Same amount of electrons

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9
Q

Which monatomic ions tend to possess the electron configuration of a noble gas?

A

Main group elements (not Group 14)

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10
Q

What is a polyatomic ion?

A

Overall charged unit of groups of joined atoms

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11
Q

What does the term ‘protonated’ mean?

A

Adding of a hydrogen ion (essentially just a proton)

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12
Q

What does the term deprotonated mean?

A

Removal of a hydrogen ion (essentially just a proton)

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13
Q

What is the empirical formulae?

A

Simplest ratio of atoms of each elements present in that compound

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14
Q

What form is the formula of an ionic compound written in?

A

Empirical formula

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15
Q

How to write an ionic compound?

A
  1. Name of positive ion (cation) first
  2. Include roman numerals if cation is a transition element
  3. Wirte name of anion (monatomic = ends with ‘ide’)
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16
Q

What do Roman numerals indicate on a transition metal?

A

Oxidation state (similar to charge on an ion) of metallic elements

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17
Q

What is an ionic lattice?

A

Regular, repeating 3-dimensional arrangement of cations and anions

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18
Q

How do ions arrange themselves in an ionic compound?

A

In the most stable configuration. Oppositely charged ions are as close together as possible. Ions of the same charge are as far apart as possible

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19
Q

What are the properties of ionic compounds?

A

Crystalline
Low volatilities
High melting and boiling points
Conduct electricity while molten or in aqueous solution (not when solid)
Some are soluble in water
Hard
Brittle

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20
Q

Why are ionic compounds crystalline?

A

Structure of lattice

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21
Q

What is the ionic radius?

A

In a crystalline ionic compound, it is the distance from the nucleus to the valence shell

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22
Q

What happens to the radius of an atom when it becomes a cation?

A

Reduces.
Loses a shell

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23
Q

What happens to the radius of an atom when it becomes an anion?

A

Enlarges.
Repel other electrons + swell atoms

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24
Q

What influences the structure of the ionic lattice?

A

Size of ionic radii
Charge of ions

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25
Q

What is volatility?

A

Measure of how readily a substance evaporates below its boiling point

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26
Q

Why do ionic compounds have high melting and boiling points?

A

Electrostatic attraction between charges is very strong. Large amounts of thermal energy are requried to separate ions

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27
Q

What is lattice enthalpy?

A

Energy needed to separate one mole of a solid ionic compound into gaseous ions under standard conditions

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28
Q

What is the formula for the lattice enthalpy of MgCl2?

A

MgCl2(s) -> Mg2+(g) + 2Cl-(g)

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29
Q

What units are lattice enthalpies measured in?

A

kJ / mol

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30
Q

What are endothermic reactions?

A

Processes that require energy

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31
Q

What are exothermic reactions?

A

processes that release energy

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32
Q

What type of reaction is a lattice enthalpy?

A

Endothermic

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33
Q

What is the relationship between ionic charge and lattice enthalpy?

A

Greater charge on ion = stronger electrostatic attraction = higher lattice enthalpy

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34
Q

What is the relationship between ionic radii and lattice enthalpy?

A

Larger ionic radii = greater separation of charges = weaker the electrostatic attraction = lower lattice enthalpy

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35
Q

What is relationship between attractive force and theoretical lattice enthalpy?

A

Attractive force ∝ theoretical lattice enthalpy ∝ (charge on cation x charge on anion) / sum of ionic radii

36
Q

What is required for a substance to conduct electricity?

A

Free moving, charged particles

37
Q

Can solid ionic compounds conduct electricity?

A

No.
the ions are held rigidly in place within the lattice and are not free to move.

38
Q

Can molten/aqeuous solutions conduct electricity?

A

Yes. Ions are free to move towards electrodes of opposite charge

39
Q

What is the solubility of a substance?

A

Maximum amount of that substance that can be dissolved in a given quantity of solvent at a given temperature

40
Q

What is a saturated solution?

A

A solution where no more solute can be dissolved at that temperature

41
Q

In an insoluble substance, the energy required to separate the ions is much greater than?

A

The energy released when the ions become hydrated

42
Q

What happens when a soluble compound dissolves in water?

A

Ionic bonds within solid lattice are broken
Hydrogen bonds between adjacent water molecules are broken
ion-dipole bonds are formed between ions adn water molecules

Ions become hydrated (solvated by water molecules)

43
Q

If two aqeuous solutions are together and form a precipitate, what has been formed?

A

An insoluble solution

44
Q

Why are ionic compounds hard?

A

Strong electrostatic attraction between cations and anions causes crystals to resist change in shape + be hard

45
Q

Why are ionic compounds brittle?

A

IF sufficient force is applied to crystalline lattice
- rows of ions will move relative to one another
- ions of like charges will become adjacent
- adjacent ions of like charge will repel each other (causing lattice to shatter)

46
Q

What are covalent substances?

A

Formed when non-metallic elements join together

47
Q

What are some traits of colavent substances?

A

Solids/liquids/gases at room temperature

Can have low melting/boiling points

Generally poor conductors of electricity and heat

48
Q

What is a covalent bond?

A

A shared pair of electrons

49
Q

How do non-metals bond together?

A

sharing one or more pairs of electrons

50
Q

What bonds two non-metals together?

A

Electrostatic attraction of two nuclei towards shared pair of electrons

51
Q

What happens if two atom nuclei are too far apart?

A

no attraction

52
Q

What does the optimal bond length involve?

A

Maximising attraction between the two positive nuclei to the shared pair of negative electrons while minimising the repulsion between two positive nuclei

53
Q

What can covalent bonds form between?

A

discrete molecules
large molecules
covalent networks

54
Q

What are discrete covalent molecules?

A

small groups of atoms held together by strong covalent bonds

55
Q

What do covalent bonds between large numbers of atoms form?

A

Large molecules such as polymers, plastics, fullerenes

56
Q

What do covalent bonds between an infinite number of atoms form?

A

Covalent networks such as graphite, diamond, silicon, etc

57
Q

What is the octet rule?

A

Tendency of atoms to achieve a full valence shell with a total of 8 electrons

58
Q

What do Lewis formulas show?

A

All valence electrons
- bonding pairs
- non-bonding pairs

59
Q

How to draw Lewis formulas of molecules and ions?

A
  1. Add up total number of valence electrons (including charges)
  2. Write atoms in order bonded
    - non-metal atom (with the lowest electronegativity = most top right of table) that forms most bonds will usually be central atom
  3. Place single covalent bonds betweeen atoms
  4. Place non-bonding electrons to the non-central atoms so that each has an octet of electrons
  5. Place any remaining on central atom
  6. Use lone pairs on non-central atoms to form double/triple bonds to ensure the central atom has an octet
  7. Draw square brackets around Lewis formula and write overall charger outside brackets at top right corner if polyatomic
60
Q

How to find element with lowest electronegativity via a periodic table?

A

Most to right

61
Q

What is the relationship between bond strength and amount of bonds?

A

More bonds (i.e. triple covalent bond) = stronger

62
Q

What is the relationship between bond strength and amount of bonds?

A

More bonds = stronger bond

63
Q

What does VSEPR stand for?

A

Valence
Shell
Electron
Pair
Repulsion

64
Q

What does the VSEPR model enable?

A

The shape of the molecules to be predited from the repulsion of electron domains around a central atom

65
Q

What is an electron domain?

A

region where electrons are likely to be found

66
Q

What can each electron domain be occupied by?

A

A single electron
Lone pair
Single bond
Double bond
Triple bond

67
Q

How are electron domains orientated?

A

As far away as possible from each other in 3D space

68
Q

What are the three electron domain geometry options?

A

Linear
Trigonal planar
Tetrahedral

69
Q

What are thre five molecular geometry options?

A

Linear
V-shaped
Trigonal planar
Trigonal pyramidal
Tetrahedral

70
Q

What is the electron domain geometry of a central atom surrounded by 4 occupied electron domains?

A

Tetrahedral

71
Q

What is the electron domain geometry of a central atom surrounded by 3 occupied electron domains?

A

Trigonal planar

72
Q

What is the electron domain geometry of a central atom surrounded by 2 occupied electron domains?

A

Linear

73
Q

What is the molecular geometry of a central atom surrounded by 4 occupied electron domains and 0 lone pairs?

A

Tetrahedral
109.5 degree bond angle

74
Q

What is the molecular geometry of a central atom surrounded by 4 occupied electron domains and 1 lone pairs?

A

Trigonal pyramidal
107 degree bond angle

75
Q

What is the molecular geometry of a central atom surrounded by 4 occupied electron domains and 2 lone pairs?

A

Bent
105 degree

76
Q

What is the molecular geometry of a central atom surrounded by 4 occupied electron domains and 3 lone pairs?

A

Linear

77
Q

What is the molecular geometry of a central atom surrounded by 3 occupied electron domains and 0 lone pairs?

A

trigonal planar

78
Q

What is the molecular geometry of a central atom surrounded by 3 occupied electron domains and 1 lone pairs?

A

V-shaped

79
Q

What is the molecular geometry of a central atom surrounded by 3 occupied electron domains and 2 lone pairs?

A

Linear

80
Q

What is the molecular geometry of a central atom surrounded by 2 occupied electron domains and 0 lone pairs?

A

Linear
180 degrees

81
Q

What is the molecular geometry of a central atom surrounded by 2 occupied electron domains and 1 lone pairs?

A

Linear

82
Q

What is the molecular formula?

A

The actual number of atoms of each element present in a covalent molecular substance

83
Q

What is the order of repulsion in terms of bonding pairs and lone pairs?

A

Least repulsed: bonding pair + bonding pair

Middle repulsed: bonding pair + lone pair

Most repulsed: lone pair + lone pair

84
Q

What is a coordination bond?

A

Covalent bond in which both the electrons of the shared pair originate from the same atom?

85
Q

How is ammonium formed?

A

NH3(aq) + H+(aq) -> NH4+ (aq)

86
Q

How to know if a coordinate bond has occured?

A

One atom will have formed more bonds that usual

IB Chemistry (7 decks)

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