Covalent bonding and Halogens - TN

Question 1

What is covalent bonding

Answer 1

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

Question 2

why does covalent bonding happen in non-metallic atoms

Answer 2

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

Question 3

what is an inter-molecular bond

Answer 3

the bond between two molecules

• eg between two H2O molecules

Question 4

what is an intra-molecular bond

Answer 4

the bond within a molecule

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

Question 5

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

Answer 5

covalent bonds

Question 6

can simple molecular substances conduct electricity

Answer 6

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

Question 7

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

Answer 7

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

Question 8

what does RMM stand for

Answer 8

Relative Molecular Mass

Question 9

what does IMF stand for

Answer 9

InterMolecular Forces

Question 10

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

Answer 10

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

Question 11

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

Answer 11

contain only a few atoms held together by covalent bonds

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

Question 12

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

Answer 12

the intramolecular bonds are strong but the intermolecular bonds are weak

Question 13

what is a molecular solid and give an example

Answer 13

a substance that is solid at room temp

eg - iodine
(Iodine sublimes with very little energy)

Question 14

all diatomic molecules have what type of bond

Answer 14

covalent bonds

Question 15

what catalyst is best for breaking down Hydrogen Peroxide

Answer 15

Manganese Oxide

Question 16

what is an allotrope

Answer 16

different arrangements of the same element

Question 17

four allotropes of carbon

Answer 17

• diamond
• graphite
• silicon dioxide
• fullerenes (buckminsterfullerene)

Question 18

what structure does a Buckminster fullerene have

Answer 18

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

Question 19

what are the two main types of covalently bonded substances

Answer 19

• simple molecules
• giant covalent structures

Question 20

what is a giant covalent structure

Answer 20

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

Question 21

melting and boiling points of each allotrope of carbon

Answer 21

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

Question 22

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

Answer 22

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

Question 23

does diamond conduct electricity (or heat)

Answer 23

no - (no free electrons)

Question 24

does graphite conduct electricity

Answer 24

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

Question 25

does silicon dioxide conduct electricity

Answer 25

no

Question 26

can a Buckminster fullerene conduct electricity

Answer 26

no

Question 27

structure of diamond

Answer 27

- GIANT COVALENT LATTICE - tetrahedral - made up of carbon atoms - extremely strong covalent bonds 4 outer electrons all used to bond with four neighbouring atoms

Question 28

structure of graphite

Answer 28

- 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

Question 29

structure of a Buckminster fullerene

Answer 29

round, cage like structure that consists of 60 carbon atoms

Question 30

structure of silicon dioxide

Answer 30

- tetrahedral - giant covalent lattice - very similar to diamond except that is is made up of silicon and oxygen atoms

Question 31

what are the group 7 elements called

Answer 31

halogens

Question 32

what group in the periodic table are the Halogens

Answer 32

group 7

Question 33

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

Answer 33

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

Question 34

why can the layers on graphite slide over each other

Answer 34

due to the weak intermolecular bonds

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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)

Question 37

What states are the Halogens at room temperature

Answer 37

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

Question 38

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

Answer 38

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

Question 39

test for chlorine

Answer 39

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

Question 40

what colour is blue litmus in acids

Answer 40

red

Question 41

how do strong acids dissociate compared to weak acids

Answer 41

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

Question 42

what is a halide

Answer 42

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

Question 43

what are the halides of iodine, chlorine and bromine

Answer 43

Iodide Chloride Bromide

Question 44

How to test for displacement in a reaction of halogens

Answer 44

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

Question 45

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

Answer 45

- very strong - the shared pair of electrons effectively pull the nuclei of the atoms closer together

Question 46

do simple molecular substances conduct electricity and why

Answer 46

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

Question 47

describe and explain the physical features of a C60 fullerene

Answer 47

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

Question 48

what is diamond used for practically

Answer 48

- cutting

Question 49

how are all the halogens bonded and with what structure

Answer 49

- covaletnly - simple molecular

Question 50

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

Answer 50

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