3 - Bonding Flashcards

1
Q

What are ionic bonds?

A

Bonds formed between elements whose atoms need to lose and gain electrons to become isoelectronic with the nearest noble gas configuration, electrons are transferred from one atom to the other.

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2
Q

What are the four chemical bonds?

A

Ionic
Covalent
Dative
Metallic

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3
Q

What is the simple definition of ionic bonding?

A

Oppositely charged ions held together in a crystal lattice by electrostatic attraction.

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4
Q

What are positive ions and their properties?

A

Cations
Formed when electrons removed
Smaller than original atom
Endothermic process

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5
Q

What are negative ions and their properties?

A

Anions.
Formed when electrons are added to the atom.
Larger than original atom due electron repulsion.
Exothermic process.

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6
Q

What is a giant ionic crystal lattice?

A

Oppositely charged ions held together in a 3D lattice by electrostatic attraction.

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7
Q

What is the definition of covalent bonding?

A

Consists of a shared pair of electrons with one electron being supplied by each atom either side of the bond.
Atoms are held together as their positively charged nuclei are attracted to the shared electrons.

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8
Q

What do covalent bonds form between?

A

Atoms of the same or different elements
Elements in group 4
Head of the group elements
High ionisation energies

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9
Q

What is the orbital theory with covalent bonds?

A

Covalent bonds are formed when orbitals with one electron each overlap, this forms a region in space where an electron pair can be found.
Greater overlap = stronger bond

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10
Q

What is sigma bond?

A

A type of covalent bond formed by two orbitals overlaping along the axis connecting the two nuclei.
Forming an area of high electron density between the nuclei.

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11
Q

What is pi bond?

A

A type of covalent bond formed from the sidways overlap of orbitals. Creating an area of high electron density above and below the nuclei.

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12
Q

Explain electron exceptions with covalent bonding?

A

Some don’t achieve an octet
Some will exceed their octet, atoms from period 3 can due to empty d orbitals.

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13
Q

What is dative covalent bonding?

A

Where both electrons in the shared pair of electrons are provided by one species.
Donor species will have lone pairs of electrons and acceptor species will not achieve an octet.

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14
Q

What is a hazard?

A

Something that may cause harm.

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15
Q

What is a risk?

A

The likelihood that someone will be harmed by the hazard.

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16
Q

What is electronegativity?

A

The power of an atom to attract the shared pair of electrons in a covalent bond.

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17
Q

What is the most electronegative atom?

A

Fluorine

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18
Q

What 3 factors affect electronegativity?

A

Nuclear charge
Atomic radius
Shielding

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19
Q

How does nuclear charge affect electronegativity?

A

An increase in protons means a stronger attraction from the nucleus to the bonding pair of electrons, increasing electronegativity.

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20
Q

How does atomic radius affect electronegativity?

A

The smaller the atomic radius the closer the bonding electrons to the nucleus, the greater the attraction, therefore the greater the electronegativity.

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21
Q

How does shielding affect electronegativity?

A

The fewer the shells, the less the shielding of the bonding electrons, therefore the stronger the attraction from the nucleus, increasing the electronegativity.

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22
Q

What is a non-polar bond?

A

When two atoms have the same/ similar electronegativity so they both pull the bonding electrons to the same extent, therefore electrons are evenly shared.

23
Q

What is a polar bond?

A

When atoms have different electronegativity, so one atom pulls the bonding electrons closer to itself, making it slightly more negative and the other more positive.
A dipole is formed.

24
Q

What are theintermolecular vs intramolecular forces?

A

Intermolecular - van der Waal’s, dipole-dipole, hydrogen bonds
Intramolecular - covalent, ionic, dative, megallic

25
Q

What are van der Waal’s forces?

A

Forces that exist between molecules as electrons move quickly in orbitals and their position is changing, so they could be anywhere in an atom.
The possibility that one side has more electrons than the other will induce a weak and fleeting dipole.

26
Q

What are dipole-dipole forces?

A

Forces that occur in polar bonds, where one atom is more electronegative.

27
Q

What is hydrogen bonding?

A

A special case of dipole-dipole interactions, which result from the attraction between a hydrogen atom covalently bonded to a very electronegative atom.
Strongest IMF due to strong permanent dipoles.

28
Q

Why does ice float on water?

A

When water freezes the H2O molecules form hydrogen bonds between each other and arrange themselves into a lattice, meaning the molecules are further apart making the hydrogen bonds stable. This means ice has a lower density than water.

29
Q

What happens when ice melts?

A

The lattice collapses slightly so the molecules pack closer together, making it more dense.

30
Q

What is electron pair repulsion theory?

A

Each pair of electrons around an atom will repel all other electrons pairs, therefore taking up positions as far away as possible to minimise repulsion.
This means the shape of a molecule depends on the number of lone and bonding pair of electrons.

31
Q

What is the shape of a molecule with 2 bonding pairs?

A

Linear
Bond angles = 180

32
Q

What is the shape of a molecule with 3 bonding pairs?

A

Trigonal planar
Bond angle = 120

33
Q

What is the shape of a molecule with 4 bonding pairs?

A

Tetrahedral
Bond angles = 109.5

34
Q

What is the shape of a molecule with 5 bonding pairs?

A

Trigonal bypyramid
Bond angles = 120, 90

35
Q

What is the shape of a molecule with 6 bonding pairs?

A

Octahedral
Bond angles = 90

36
Q

What is a lone pair?

A

A pair of unpaired valence electrons.

37
Q

Explain the repulsion between bonding and lone pair of electrons in a covalent bond?

A

The bonding pair is attracted to both atoms nucleus, the lone pair is only attracted to its own atoms nucleus.
Therefore the lone pair is pulled closer to the atoms nucleus, ,meaning the repulsion between the lone pair and bonding pair is greater than the repulsion between bonding pairs.
So lone pairs decrease bond angles by 2.5

38
Q

What is the shape of a molecule with 2 bonding pairs and 2 lone pairs?

A

Angular
Bond angles = 104.5

39
Q

What is the shape of a molecule with 3 bonding pairs and 1 lone pairs?

A

Pyramidal
Bond angles = 107

40
Q

What is the shape of a molecule with 4 bonding pairs and 2 lone pairs?

A

Square planar
Lone pairs 180
Bond angles = 90

41
Q

What effect does double bonds have on the shape of molecules?

A

No effect, as double bonds repel the same as single bonds.

42
Q

What is a crystal?

A

A solid with a regular arrangement, held together by forces of attraction.

43
Q

What are ionic crystals?

A

Strong electrostatic attraction between oppositely charged ions.

44
Q

What are properties of ionic crystals?

A

High melting points, due to strong attraction.

45
Q

What are metallic crystals?

A

Lattice of positive ions embedded in a sea of delocalised electrons.

46
Q

What are properties of metallic crystals?

A

High melting point, due to strong electrostatic attraction throughout.

47
Q

What are molecular crystals?

A

Molecules held in a regular array by intermolecular forces, covalent bonds within the molecules.

48
Q

What are properties of molecular crystals?

A

Low melting point, due to weak intermolecular forces between molecules.
Don’t conduct electricity as no charged particles.

49
Q

What are macromolecular crystals?

A

When covalent bonds extent throughout a compound.
Have high melting point due to strong covalent bonds throughout

50
Q

Explain the stricture of diamond?

A

Each carbon forms 4 covalent bonds with other carbons.
The electron pairs repel each other, forming a tetrahedron.
Is a 3D lattice

51
Q

What are properties of diamond?

A

Very hard
High melting point
Don’t conduct electricity, due to no free particles.

52
Q

What is the structure of graphite?

A

Each carbon forms 3 covalent bonds with other carbon atoms. The electron pairs repel each other, forming a 2D layer (graphene) which is stacked on one another.
Each carbon atom has a spare electron in the p orbital.

53
Q

What are the properties of graphite?

A

High melting point
Soft as layers free to slide
Conducts electricity due to free electrons.