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A-level AQA Chemistry > Physical: Bonding > Flashcards

Physical: Bonding Flashcards

1
Q

What are the three types of bonding?

A

ionic
metallic
covalent

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2
Q

Do ionic substances have high mp/bp?

A

yes, due to the strong electrostatic forces of attraction between oppositely charged ions acting in all directions so more energy is required to break the bonds

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3
Q

Do ionic substances conduct electricity?

A

when molten/in an aqueous solution

this is because the ions become free to move and carry charge

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4
Q

Are ionic substances strong?

A

yes, because the ionic bonds are strong and the ions are arranged in an ionic crystal lattice

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5
Q

Are ionic substances soluble?

A

yes, because the ions are attracted to the polar aspects of water

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6
Q

Do metallic substances have high mp/bp?

A

yes, due to the strong electrostatic forces of attraction between the delocalised electrons and the central positive metal ions in lattice

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7
Q

How does metallic bond strength increase?

A

greater the charge of the ion, the stronger the metallic bonds because the ion is stronger so the electrostatic attraction to the delocalised electrons is stronger so more energy is required to overcome the forces of attraction

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8
Q

Do metals conduct electricity?

A

yes, because the delocalised electrons are free to carry charge

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9
Q

Are metals soluble?

A

no, because there is no polar aspect to metallic substances

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10
Q

Do giant covalent substances have a high mp/bp?

A

MANY. STRONG covalent bonds between all atoms

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11
Q

Do giant covalent substances conduct electricity?

A

no because there are no free electrons or mobile ions carry charge

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12
Q

Do simple molecules have high mp/bp?

A

no. because intermolecular forces are weak between the molecules, so less energy is required to break the bonds so not a lot of energy is required to overcome the forces

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13
Q

What is covalent bonding?

A

the sharing of one or more PAIRs of electrons between non-metals

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14
Q

What is the A-level rule for covalent bonding?

A

central atoms can promote electrons between orbitals in the same principal energy level
but this promotion requires energy

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15
Q

How can you tell how many covalent bonds the central atom will make?

A

number of unpaired e⁻ = number of bonds that atom can make

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16
Q

What are lone pairs?

A

the unbonded pairs of e⁻ in the outer shell

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17
Q

Why are lone pairs more repulsive?

A

bonding pairs are stabilized between two atoms. Since there’s no atom on the other end of a lone pair, it spreads out more. So they repel more because the charge density is spread out more

18
Q

What is the name of the molecule which has 2 bonding pairs and no lone pairs and its bond angle?

A

linear

180

19
Q

What is the name of the molecule which has 3bp and no lp and its bond angle?

A

trigonal planar

120

20
Q

What is the name of the molecule which has 2bp/1lp and its bond angle?

A

bent

117

21
Q

What is the name of the molecule which has 4pb/0lp and its bond angle?

A

tetrahedral

109.5

22
Q

What is the name of the molecule which has 3bp/1lp and its bond angle?

A

trigonal pyramidal

107

23
Q

What is the name of the molecule which has 2pb/2lp/bond angle?

A

bent

104

24
Q

What is the name of the molecule which has 5pb/bond angle?

A

trigonal bipyramidal
120 equatorial bonds (makes an equator)
90 axial bonds (face to or away from you)

25
Q

What is the name of the molecule which has 6bp/bond angle?

A

octahedral

90

26
Q

What is the name of the molecule which has 4pb/2lp/bond angle?

A

square planar

90

27
Q

When drawing lone pairs in a mol, how should they be displayed?

A

in a charge cloud

28
Q

What is a dative covalent bond?

A

-when the shared pair of electrons in the covalent bond
come from only one of the bonding atoms.
-is also called co-ordinate bonding

29
Q

When is ionic bonding stronger?

A

Ionic bonding is stronger and the melting points higher when the ions are smaller and/ or have higher
charges.

30
Q

How do you explain molecular shapes? (5 steps)

A
  1. State number of bonding pairs and lone pairs of electrons.
  2. State that electron pairs repel and try to get as far apart as possible (or to a position of minimum repulsion.)
  3. If there are no lone pairs state that the electron pairs repel equally
  4. If there are lone pairs of electrons, then state that lone pairs repel more than bonding pairs.
  5. State actual shape and bond angle.
31
Q

What is VSEPR theory?

A

electron pairs arrange themselves as far apart as possible to minimise repulsion
lp to lp repulsion is greater than bp to bp repulsion

32
Q

Explain how electron pair repulsion theory can be used to deduce the shape/bond angle of PF₃

A
  1. P has 5 outer e⁻, 3e⁻ from 3 fluorine, total of 8e⁻ in outer shell, so 3pb/1lp
  2. e⁻ pairs arrange themselves as far apart as possible to minimise repulsion, lp to lp repulsion is greater than bp/bp repulsion
  3. 4 charge centres (3bp/1lp) so it is based on tetrahedral shape, bu due to VSEPR theory, angle reduced from 109.5 to 107
33
Q

Draw the structure of TlCl₄³⁻

A

Tl centre
4 Cl
3 of Tl’s outer e⁻ bonds to 3 Cl
the three extra outer e⁻: one bonded to 4th Cl and the other two are a lone pair
square brackets surrounding whole structure

34
Q

Write an equation to show the formation of Tl (1) Bromide from its elements

A

Tl + 1/2Br₂ ——> TlBr
use state symbols: Tl is a solid, Br is a liquid and TlBr is a solid
cannot change the number of the product!!!!

35
Q

What is electronegativity?

A

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

36
Q

How does electronegativity change across a period and down a group?

A

electronegativity increases across a period due to increased nuclear charge
it decreases down a group because the atomic radius increases so nuclear attraction decreases

37
Q

How is a temporary dipole formed?

A

when atoms in a molecule have the same electronegativities , then the electrons are distributed evenly but because electrons are always moving, at times, e⁻ maybe located more on one side, which will repel e⁻ on the other side. creating a slightly charged side to the mol., this is a temporary dipole (temp. polar bond)

38
Q

How is a permanent dipole formed?

A

when there are differences in electronegativity, it causes bonds to become polarised, which results in a dipole which isn’t cancelled out so the mol. will be polar

39
Q

What is a dipole?

A

a difference in charge between two atoms

40
Q

Are symmetrical molecules with polar bonds polar molecules?

A

no, they are overall non-polar, because if the polar bonds are arranged symmetrically, the dipoles cancel each other out

A-level AQA Chemistry (9 decks)

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