Chemical Bonding: Covalent Bonding Flashcards

1
Q

what is covalent bonding?

A

attraction between the shared pair of negative electrons and the positive nuclei either side of it

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2
Q

when does covalent bonding occur?

A

occurs between two non-metals (groups 4,5,6,7)

occurs in solids, liquids and gases (at room temperature)

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3
Q

do covalent bonds conduct electricity and why

A

no

Electrons are shared to complete the outer shell

they can’t move therefore doesn’t conduct electricity

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4
Q

how are covalent bonds represented?

A

with dot and cross diagrams

usually only draw outside shells but unless this is specified it is safer to draw all the shells

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5
Q

what are the bonds between hydrogen atoms

A

very strong covalent bonds

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6
Q

what do molecules have?

A

a certain fixed number of particles

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7
Q

what are hydrogen molecules

A

diatomic

(contains two molecules)

H2

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8
Q

what is released when bonds are formed

A

energy

makes things involved more stable

the more bonds and atom can form, the more energy released, the more stable the bond becomes

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9
Q

if hydrogen atom bonds with another hydrogen atom is it less or more stable

A

more stable

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10
Q

when hydrogen and chlorine bond together what molecule do they form

A

a hydrogen chloride molecule

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11
Q

what type of bond is formed in a hydrogen chloride molecule and what is its diagram

A

covalent bond

Chlorine has one unpaired electron on outer shell

Hydrogen has one unpaired electron on outer shell

Both atoms bond together and form a covalent bond

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12
Q

what is the significance of noble gas structures

A

ehen atoms bond covalently, they often produce outer electronic structures the same as noble gases

there are also lots of examples that look nothing like noble gas structures

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13
Q

what is the symbol for a chlorine molecule

A

Cl2

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14
Q

what bond is formed in a chlorine molecule and what is its diagram

A

a covalent bond

each chlorine has an unpaired electron which is shared between the two chlorine atoms

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15
Q

what type of bond do each methane, ammonia and water form

A

covalent bonds

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16
Q

what is the sybol and diagram for methane

A

symbol = CH4

the carbon atom has four unpaired electrons

they share one electron from four hydrogen atoms

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17
Q

what is they symbol and diagram for ammonia

A

the nitrogen atoms has three unpaired electrons

they share one electron from three hydrogen atoms

symbol = NH3

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18
Q

what is the symbol and diagram for water?

A

symbol = H2​O

there are two unpaired electrons on the oxygen atom

they bond with two hydrogen atomssymbol = H2O

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19
Q

what bonding is similar to that of methane and what is different?

A

ethane

there is a carbon-carbon bond also

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20
Q

what is the symbol and diagram for ethane?

A

symbol = C2H6

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21
Q

how many electrons are shared by each atom in single covalent bonding?

A

one

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22
Q

how many electrons are shared by each atom in double covalent bonding?

A

two

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23
Q

how many electrons are shared by each atoms in triple covalent bonding?

A

three

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24
Q

what type of covalent bonding is formed in carbon dioxide and what is its diagram

A

double

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25
Q

what type of covalent bonding in nitrogen and what is its diagram

A

triple

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26
Q

what is special about the structure of sodium hydroxide?

what is its diagram?

A

you have Na (a metal) and OH (a non-metal) - this makes it ionic

however, the O and H are both non-metals and that makes it covalent

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27
Q

what two types of structures are there in covalent bonding?

A

giant covalent

simple molecular

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28
Q

what type of bonding is simple molecular

A

covalent

29
Q

what state of matter do simple molecular substances tend to be?

A

gases and liquids

30
Q

how many atoms are bonded together in simple molecular structures

A

2 or 3 atoms bonded together

(simple molecules)

31
Q

how are the atoms in simple molecular substances attracted to each other

A

attracted to each other through intermolecular force

this is a weak attractive force between two or more molecules

32
Q

do simple molecular substances have high or low melting and boiling points

A

low

33
Q

do simple molecular substances conduct electricity and why

A

do not conduct electricity

molecules don’t have any overall electrical charge

there are no electrons that can move from molecule to molecule

34
Q

do simple molecular substances tend to be soluble or insoluble in water and why?

A

insoluble (unless they react with it)

due to their size, water molecules have stronger intermolecular attractions between them than you might think

attractions need to be broken for a substance to dissolve so that the dissolving molecules can fit between them

any new attractions between water molecules and the covalent molecules are not usually big enough to make up for this

35
Q

are simple molecular substances often organic solvents or not and why

A

yes

intermolecular attractions between the two different types of molecule are much the same as in the pure substances

36
Q

in water, how do you break the intermolecular forces?

A

by heating

37
Q

does iodine crystal form a simple molecular structure or a giant covalent lattice?

what does its formation look like?

A

simple molecular

38
Q

does water form a simple molecular structure or a giant covalent lattice?

what does its formation look like?

A

simple molecular

39
Q

what state of matter are giant covalent structures?

A

mainly solids

40
Q

are there intermolecular forces in giant covalent structures? why?

A

no

only strong covalent bonds which need lots of energy to break

(except graphite)

41
Q

what are some common properties of giant covalent structures?

A

Very high melting points and boiling points

Solid, crystalline, hard

Do not conduct electricity

42
Q

what does the giant covalent lattice of silicon dioxide (sand) SiO2 look like?

A
43
Q

does diamond form a simple molecular structure or a giant covalent structure?

A

giant covalent structure

44
Q

what is diamonds relationship with carbon?

A

it is a pure form of carbon

45
Q

what is the structure of diamond?

A

each carbon atom has four unpaired electrons on its outer shell

each carbon atoms bonds strongly to four other carbon atoms and each carbon forms four covalent bonds

tetrahedral arrangement which continues on and on in three dimensions

46
Q

is diamond a molecule? why?

A

not a molecule because atoms joined up in a real diamond is completely variable (depends on size of crystal)

molecules always contain a fixed number of atoms joined by covalent bonds

47
Q

is graphite a giant covalent structure or a simple molecular structure?

A

giant covalent

48
Q

is graphite a form of carbon?

A

yes

49
Q

what is the structure of graphite like

A

3-D lattice structure

has a layer structure

layers slide easily over each other

50
Q

why is graphite soft with a slimy feel?

A

layers easily slide over each other

mixed with clay to make pencils

pure graphite is used as dry lubricant

51
Q

why does graphite have a high melting point, boiling point and is soluble in any solvents

A

to melt or dissolve graphite you need to break the whole structure, including the covalent bonds, not just the layers

very large amounts of energy needed as bonds are very strong

52
Q

why is graphite less dense than diamond?

A

the layers in graphite are relatively far apart

distance between graphite layers is more than twice the distance between atoms in each layer

graphite cyrstal contains a lot of water space, whereas there is none in a diamond crystal

53
Q

why does graphite conduct electricity?

A

each carbon atom is only joined to three others

one electron drops between the layers and becomes delocalised

this electron is free to move around the layer

54
Q

what are intermolecular forces

A

forces of attractions between separate molecules

55
Q

are intermolecular bonds are weaker/stronger than ionic or covalent bonds

A

much weaker

they vary in strength from substance to substance

56
Q

how do intermolecular forces work?

A

the slightly positive end of one molecule attracts the slightly negative end of a neighbouring molecule

57
Q

what will heating do to intermolecular forces?

A

will supply energy to break these intermolecular attractions

causes the substance to either melt or boil

doesn’t take much heat energy to break intermolecular attractions

58
Q

what does melting do to intermolecular forces?

A

some but not all intermolecular forces are broken

59
Q

what does boiling do to intermolecular forces?

A

the attractions are completely disrupted and the molecules become free to move around as a gas

60
Q

do melting or boiling break the covalent bonds?

A

no

break intermolecular forces not the covalent bonds

61
Q

where do intramolecular forces occur?

A

occurs in both simple molecular and giant covalent bonds

inside the molecules, attraction between atoms

62
Q

what is the diagram for F2

A
63
Q

what is the diagram for H2S

A
64
Q

what is the diagram for CH4

A
65
Q

what is the diagram for PH3

A
66
Q

what is the diagram for SiCl4

A
67
Q

what is the diagram for C2H6

A
68
Q

what is the difference between simple molecular substances and giant covelant structures?

A

check this