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Chemistry > Covalent bonding and Halogens - TN > Flashcards

Covalent bonding and Halogens - TN Flashcards

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1
Q

What is covalent bonding

A
  • the electrostatic force of attraction between a shared pair of electrons and positively charged nuclei of bonding atoms
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2
Q

why does covalent bonding happen in non-metallic atoms

A

so that they can forms bonds to create a full outer shell

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3
Q

what is an inter-molecular bond

A

the bond between two molecules

  • eg between two H2O molecules
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4
Q

what is an intra-molecular bond

A

the bond within a molecule

  • eg the bond between on of the H and the O atom in H2O
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5
Q

what type of bonds does a simple molecule contain (simple molecular structure)

A

covalent bonds

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6
Q

can simple molecular substances conduct electricity

A

no - they have no overall charge or charged particles that can separate
- not even when liquid or dissolved in water

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7
Q

do simple molecular substances have high or low melt and boil points

A

low - the weak forces of attraction are broken by very little energy

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8
Q

what does RMM stand for

A

Relative Molecular Mass

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9
Q

what does IMF stand for

A

InterMolecular Forces

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10
Q

why do the melting and boiling points of simple molecular substances increase (in general) with RMM

A

This is because larger molecules have more forces of attraction between them which must be overcome

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11
Q

what is a simple covalent structure/ simple molecular substance
Give examples

A

contain only a few atoms held together by covalent bonds

eg - water, ammonia, methane, carbon dioxide, chlorine and hydrogen

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12
Q

are the different bonds within a covalent structure strong or weak?

A

the intramolecular bonds are strong but the intermolecular bonds are weak

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13
Q

what is a molecular solid and give an example

A

a substance that is solid at room temp

eg - iodine
(Iodine sublimes with very little energy)

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14
Q

all diatomic molecules have what type of bond

A

covalent bonds

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15
Q

what catalyst is best for breaking down Hydrogen Peroxide

A

Manganese Oxide

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16
Q

what is an allotrope

A

different arrangements of the same element

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17
Q

four allotropes of carbon

A
  • diamond
  • graphite
  • silicon dioxide
  • fullerenes (buckminsterfullerene)
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18
Q

what structure does a Buckminster fullerene have

A

60 carbon atoms each bonded to three others by two single bonds and a double

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19
Q

what are the two main types of covalently bonded substances

A
  • simple molecules
  • giant covalent structures
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20
Q

what is a giant covalent structure

A

a three-dimensional structure of atoms that are joined by covalent bonds

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21
Q

melting and boiling points of each allotrope of carbon

A

Diamond - very high
Graphite - high
Silicon dioxide - high
Buckminsterfullerene - low

22
Q

why do graphite, diamond, and silicon dioxide have high melting and boiling points

A

because a lot of strong covalent bonds must be broken (high molecular mass)

23
Q

does diamond conduct electricity (or heat)

A

no - (no free electrons)

24
Q

does graphite conduct electricity

A

yes - it only uses 3 of its electrons to bond so each atom has one delocalised electron that is free to move throughout the structure

25
Q

does silicon dioxide conduct electricity

A

no

26
Q

can a Buckminster fullerene conduct electricity

A

no

27
Q

structure of diamond

A
  • GIANT COVALENT LATTICE
  • tetrahedral
  • made up of carbon atoms
  • extremely strong covalent bonds

4 outer electrons all used to bond with four neighbouring atoms

28
Q

structure of graphite

A
  • EXISTS IN LAYERS
  • covalent bonds between carbon atoms are strong but intermolecular bonds between layers are weak (so brittle)
  • each carbon atom is bonded to only three others (rather than four)

layers able to slide over each other

29
Q

structure of a Buckminster fullerene

A

round, cage like structure that consists of 60 carbon atoms

30
Q

structure of silicon dioxide

A
  • tetrahedral
  • giant covalent lattice
  • very similar to diamond except that is is made up of silicon and oxygen atoms
31
Q

what are the group 7 elements called

A

halogens

32
Q

what group in the periodic table are the Halogens

A

group 7

33
Q

explain the reactivity of the halogens as you go down the group

A

as you go down, ATOMIC SIZE INCREASES so there is a LARGER DISTANCE between outer shell and nucleus, resulting in INCREASED SHIELDING. This means that ATTRACTION DECREASES so they are less able to attract another electron to complete its outer shell

34
Q

why can the layers on graphite slide over each other

A

due to the weak intermolecular bonds

35
Q

would you expect CHCl3 or CCl4 to have a higher boiling point

A

CCl4 - it has a greater molecular mass so the strength of the intermolecular forces are greater

36
Q

what colours are the halogens: F, Cl, Br, I, At

A

F - Pale yellow
Cl - Green/yellow
Br - orange
I - grey(when solid) but purple(when vapour)
At - black (when solid) but dark purple (when vapour)

37
Q

What states are the Halogens at room temperature

A

F - gas
Cl - gas
Br - liquid
I - solid
At - solid

38
Q

explain the melting point trend of the halogens as you go down the group

A

The melting points increase as the Relative Molecular Mass increases. This means the inter-molecular forces get stronger so more energy is needed to break them down

39
Q

test for chlorine

A

blue litmus being bleached white - this us because the chlorine acts as a bleaching agent so it removes the colour from the paper

40
Q

what colour is blue litmus in acids

A

red

41
Q

how do strong acids dissociate compared to weak acids

A

a strong acid dissociates fully into its ions
a weak acid will only partially break up

42
Q

what is a halide

A

The resulting compound when halogens combine with other elements. they are formed when they gain an electron

eg NaCl

43
Q

what are the halides of iodine, chlorine and bromine

A

Iodide
Chloride
Bromide

44
Q

How to test for displacement in a reaction of halogens

A

If there is a displacement occurring there will be a colour change

you can then add cyclohexane and observe the colour of the top layer

45
Q

how strong is the force of attraction between covalently bonded molecules and why

A
  • very strong
  • the shared pair of electrons effectively pull the nuclei of the atoms closer together
46
Q

do simple molecular substances conduct electricity and why

A

no - because there are no charged particles as the molecules are neutral

47
Q

describe and explain the physical features of a C60 fullerene

A

soft and slippery because the molecules can roll over each other easily

48
Q

what is diamond used for practically

A
  • cutting
49
Q

how are all the halogens bonded and with what structure

A
  • covaletnly
  • simple molecular
50
Q

how does Hydrogen Chloride (HCl [g]) become Hydrochloric acid (HCl[aq])

A
  • HCl(g) is dissolved in water to form HCl(aq)
  • this dissociates to form H+
  • the H+ is acidic

Chemistry (30 decks)

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