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A level Chemistry Paper 1- Foundations in Chemsitry > Bonding and structure > Flashcards

Bonding and structure Flashcards

1
Q

What is a simple covalent molecule?

A

2 or more non metal atoms bonded

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2
Q

What is a giant covalent molecule?

A

Diamond
Graphite
Boron
Silicon
Silicon dioxide

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3
Q

What is a giant ionic lattice?

A

a metal and a non metal bonded

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4
Q

What is a giant metallic lattice?

A

the elements of the periodic table

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5
Q

What is a covalent bond?

A

The strong electrostatic force of attraction between a shared pair of electrons and the nuclei of the bonded atoms

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6
Q

What happens when electrons are shared?

A

A bond is formed (covalent)

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7
Q

What is a dative covalent bond?

A

a covalent bond where only one of the bonded atoms donates both electrons being shared

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8
Q

What is the shape and angle for 2 bonding pairs and no lone pairs?

A

Linear- 180 degrees

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9
Q

What is the shape and angle for 3 bonding pairs and no lone pairs?

A

trigonal planar- 120 degrees

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10
Q

What is the shape and angle for 4 bonding pairs?

A

tetrahedral- 109.5

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11
Q

What is the shape and angle for6 bonding pairs and no lone pairs?

A

90 degrees- octahedral

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12
Q

What is the shape and angle for 3 bonding pairs and 1 lone pair?

A

pyramidal- 107

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13
Q

What is the shape and angle for 2 bonding pairs and 2 lone pairs?

A

bent/ v shaped- 104.5

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14
Q

How do you explain the shape of a covalent molecule?

A
  1. State the number of bonding and lone pairs
  2. State electron pairs repel and try get as fair away as possible
    3.If there are no lone pairs then state that the electron pairs will repel equally
  3. If there are lone pairs of electrons then state that the lone pairs repel more that the bonding pairs
  4. State the actual shape and bond angle
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15
Q

What do molecules that have a lone pair of electrons often act as?

A

A base

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16
Q

What is a base?

A

A base is a proton acceptor

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17
Q

What is an example of a base?

A

When ammonia acts as a base it accepts the H+ ion to form a dative covalent bond forming the ammonium ion .

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18
Q

What happens as a result of lone pairs repelling more than the bonding pairs?

A

they reduce the bond angles (by 2.5)

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19
Q

What can water sometimes act as?

A

A base

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20
Q

What is a systematic way of working out the shape of a negative molecular ion?

A

-Use periodic table to decide how many outer shell electrons the central atom has
-Draw dot and cross diagram. Add 1 extra electron to the central atom to account for the negative charge in the ion
-Decide how many lone pairs are present and how many bonding pairs

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21
Q

What is the difference in repulsion for single bonds and multiple bonds?

A

They repel each other in the same way that singles do but less than lone pairs

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22
Q

Where do covalent bonds occur?

A

Simple covalent substances

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23
Q

What are induced dipole interactions?

A

Temporary induced dipole dipole forces and they occur between non-polar molecules

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24
Q

How do induce dipole dipole interactions arise?

A

-electrons in the molecule are constantly moving and anyone instant electron distribution may become unsymmetrical
-Produces temporary dipole in that molecule
-if another molecule approaches it with the temporary dipole and opposite dipole is induced to the adjacent molecule

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25
Q

Why do induced dipole dipole interactions only act for a short time?

A

The electrons density is constantly changing

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26
Q

what is the weakest intermolecular force?

A

induced dipole dipole- Typically, about one percent of the strength of a covalent bond

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27
Q

what does symmetrical molecules with no overall dipole interact through?

A

induced dipole dipole (non polar)

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28
Q

what can the increasing boiling points of the alkane homologous series? Be explained by?

A

increase in the number of electrons in the bigger molecules, causing an increase in the induced dipole dipole interactions between neighbouring molecules

29
Q

when does the strength of induced dipole dipole interactions increase?

A

-as the number of electrons in the molecule or atom increases (a chance that temporary dipoles will form)
-surface contact of the molecules or atom increases for example, long chain alkanes have a larger surface contact

30
Q

When do permanent dipole dipole interactions occur?

A

In addition to induced dipole, dipole interactions

31
Q

What does it mean as permanent dipole dipole interaction are stronger than induced dipole dipole interactions?

A

The compounds have higher boiling points

32
Q

What is electronegativity?

A

The ability of an atom to attract the bonding electrons in a covalent bond

33
Q

What is a dipole?

A

The separation of charge in a bond, which occurs as a result of these differences in electronegativity

34
Q

What are the most electronegative atoms?

A

F N O Cl

35
Q

what is the difference in electronegativity in hydrogen and carbon?

A

Very little

36
Q

why does electronegativity increase across the period?

A

The number of protons increase and the atomic radius decreases, because the electrons in the same shell are pulled more

37
Q

Why does electronegativity decrease down the group?

A

because the distance between the nucleus and outer electrons increases, and the shielding of in a shell electrons increase

38
Q

What do erase more differences in electronegativity do?

A

do not produce significant dipoles

39
Q

when do polar molecules occur?

A

When atoms with different electronegativities bond, have permanent dipole, and the molecule is unsymmetrical

40
Q

when does a polar bond occur?

A

When does an unequal distribution of electrons in a bond and charge separation is produced

41
Q

What is a symmetrical molecule?

A

all the atoms are on the central atom are the same, and there are no lone pairs on the central atom- therefore dipole cancel each other out, and the molecule has no overall dipole

42
Q

how do dipole act if the molecule is symmetrical?

A

in the opposite directions

43
Q

What is the definition of hydrogen bonding?

A

As intermolecular bonding between molecules, contain N O or F and the h of NH OH or HF

44
Q

what is the strongest intermolecular force?

A

Hydrogen bonding, which occurs in addition to induce dipole dipole interactions

45
Q

what is the atom with the lowest electronegativity

A

Caesium or francium

46
Q

what are the anomalously high boiling points of water, ammonia and HF caused by?

A

Hydrogen bonding between the molecules

47
Q

What does the large difference in electronegativity between the hydrogen atom and either a nitrogen, oxygen or fluorine atom mean?

A

that very polar bonds are formed with the hydrogen having a strong partial charge (dipole +)

48
Q

Why can water form two bonds per molecule?

A

Because oxygen is very electronegative, and it has two lone pairs

49
Q

why does ice have low density?

A

The molecules are held further apart than in liquid water (The water molecules form hydrogen bonds between each other and arranged themselves into an open lattice structure)

50
Q

what is the common cause for anomalous properties?

A

Hydrogen bonding

51
Q

what is melting/boiling point in covalent substances determined by?

A

Type and strength of bond/intermolecular force being broken

52
Q

What is electrical conductivity in covalent substances determined by?

A

The presence or absence of mobile charge carriers

53
Q

What is water, solubility and covenant substances, determined by?

A

The strength of interactions with the water molecules

54
Q

Why do simple materials have low melting/boiling points?

A

-molecules are held together by weak intermolecular forces (IDD, PDD) these require a little energy to overcome
-Atoms are held together by strong Covalent bonds, but these are not broken when boiled/melted

55
Q

What is the conductivity in simple covalent molecules?

A

no mobile charge, carriers and so don’t conduct electricity

56
Q

What is a solubility for simple, covalent materials?

A

Nonpolar substances can’t interact with water molecules so tend to be insoluble in water

57
Q

why do giant covalent materials have high boiling and melting points?

A

They are held together by strong covalent bonds, which require a large amount of energy to break

58
Q

Which are the two covalent materials, that conduct electricity?

A

graphite and graphene- they have delocalised electrons

59
Q

Why are giant covalent materials insoluble in water?

A

They do not interact with water molecules

60
Q

Why do giant metallic materials have high, melting and boiling points?

A

-they have strong, electrostatic attractions held together by ions and delocalised electrons
-The strong bonds require a lot of energy to break

61
Q

When can giant metallic materials conduct electricity?

A

when molten or liquid- mobile electrons

62
Q

Why are giant metallic substances soluble in water?

A

They do not interact with water molecules

63
Q

what is the definition of a giant metallic bond?

A

The strong electrostatic attraction between cations and the delocalised electrons

64
Q

what is an ionic bond?

A

electrostatic force of attraction between oppositely charged ions formed by electron transfer

65
Q

why do giant ionic materials have a high melting point?

A

oppositely charged ions together by strong ionic bonds, which require a large amount of energy to break

66
Q

when do solid ions not conduct, electricity?

A

When they are in a fixed regular lattice

67
Q

When do ionic materials conduct electricity?

A

when molten or in a solution- ions are mobile so substances will conduct

68
Q

why are giant ionic substances soluble in water?

A

They disassociate into ions, which can interact with the polar water molecules

69
Q

What are two anomalous properties water in terms of h2 bonding?

A

Higher bp- strong hydrogen bonds
Ice less dense than water- hydrogen l bonds hold water molecules far apart in an open lattice

A level Chemistry Paper 1- Foundations in Chemsitry (7 decks)

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