3 - bonding Flashcards
(119 cards)
1
Q
what do bonds between atoms always involve
A
their outer electrons
2
Q
why are noble gases very unreactive
A
they have full outer shells
3
Q
what happens when atoms bond together
A
they share or transfer electrons to achieve a more stable electron arrangement, often a full out main level of electrons like the noble gases
4
Q
what are the three types of strong chemical bonds
A
ionic, covalent, and metallic
5
Q
what is the easiest way for metals to attain a full outer shell
A
lose their outer electrons
6
Q
how many electrons do metals have in their outer shell
A
1,2,or 3
7
Q
what is the easiest way for non-metals to gain full outer shell
A
gain electrons
8
Q
when does ionic bonding occur
A
between metals and non-metals
9
Q
ionic bonding
A
electrons are transferred from metal atoms to non-metal atoms, psitive and negative ions are formed
10
Q
what is ionic bonding the result of
A
electrostatic attraction betwee oppositely charged ions
11
Q
what struture do ionic compounds always exist in
A
a lattice
12
Q
properties of ionic compounds
A
- solid at room temperature
- giant structures
- high melting temperatures
13
Q
why do ionic compounds have high melting points
A
because in order to melt an ionic compound, energy must be supplied to break up the lattice of ions
14
Q
why can ionic compounds conduct electricity when molten or dissolved in what but not solid
A
because the ions that carry the current are free to move in the liquid state but are not free in the solid state
15
Q
why are ionic compounds brittle and shatter easily
A
because they form a lattice of alternating positive and negative ions, so movement produces contact between ions with like charges
16
Q
what do non metals need to do to fill their outer shell
A
recieve electrons
17
Q
when does a covalent bond form
A
between 2 non-metal atoms
18
Q
what happens in a covalent bond
A
the atoms share some of their outer electrons so that each atom has a full outer shell
19
Q
what is a covalent bond
A
a shared pair of electrons
20
Q
what is a small group of covalently bonded atoms called
A
a molecule
21
Q
what can you represent a covalent bond with
A
a single line between two atoms
22
Q
what are atoms with covalent bonds held together by
A
the electrostatic attraction between the nuclei and the shared electrons, which takes place within the molecule
23
Q
how many electrons are shared in a double bond
A
4 electrons
24
Q
why can covalently bonded molecules occur in any state
A
because the strong covalent bonds are only betwee the atoms within the molecules there is only weak attraction betwee the molecules so the molecules do not need much energy to move apart from each other
25
why are covalently bonded molecules poor conductors of electricity
because the moleucles are neutral overall. meaning there are no charged particles to carry the current
26
what is coordinate bonding
when the atoms that accepts the electron pair is an atom that does not have a full outer shell and the atom donating has a lone pair
27
lone pair
a pair of electrons that is not being used in a bond
28
what are metals
shiny elements made up of atoms that can easily lose up to three outer electrons leaving positive metal ions
29
what can the atoms in a metal element not do
transfer electrons unless there is a non-metal atom present to receive them
30
what do metals consist of
a lattice of positive ions existing in a sea of outer electrons which are delocalised
31
what happens in a metal
the positive ions tend to repel one another and this is balanced by the electrostatic attraction of these positive ions for the negatively charged sea of delocalised electrons
32
what does the number of delocalised electrons depend on
how many electrons have been lost by each atom
33
why do metals have giant structures
metallic bonding spreads throughout
34
why are metals good conductors of electricty
because the delocalised electrons can carry a current
35
why are metals good conductors of heat
they have high thermal conductivities due to the sea of electrons with energy also spread by increasing vigorous vibrations of the closely packed ions
36
what does the strength of a metallic bond depend on
the charge and size of the ion
37
why does charge affect a metallic bond
the greater the charge on the ion, the greater the number of delocalised electrons and the stronger the electrostatic attraction between the positive ions and the electrons
38
why does the size of the ion effect a metallic bond
the smaller the ion, the closer the electrons are to the positive nucleus and the stronger the bond
39
why do metals tend to be strong
the delocalised electron extend throughout the solid so there are no individual bonds to break
40
why are metals malleable and ductile
because after a small distortion, each metal ion is still in exactly the same environment as before so the new shape is retained
41
why do metals have high melting and boiling points
because they have giant structures. there is strong attraction between metal ions and the delocalised sea of electrons making the atoms difficult to seperate
42
what are the forces that hold atoms together about
the attraction of positive charges to negative charges
43
electronegativity
the power of an atom to attract the electron density in a covalent bond towards itself
44
electron density
the negative charge distribution in a molecule
45
the pauling scale
a measure of electronegativity, 0-4, the greater the number the more electronegative the atom
46
what does electronegativity depend on
the nuclear charge
the distance between the nucleus and the outer shell electrons
the shielding of the nuclear charge by electrons in inner shells
47
how does size of the atom effect electronegativity
the smaller the atom the closer to the nucleus is to the outer electronss and the greater its electronegativity
48
how does nuclear charge affect electronegativity
the larger the nuclear charge the greater the electronegativity
49
what happens to electronegativity as we go up a group in the periodic table
increases, as there is less shielding by electrons in inner shells
50
what happens to electronegativity as we go accross a period in the periodic table
increases, the nuclear charge increases, the number of inner shells remain the same and the atoms become smaller
51
where are the most electronegative atoms found
at the top right corner of the periodic table
52
what are the most electronegative atoms
-fluorine
oxygen
nitrogen
chlorine
53
what is polarity
the unequal sharing of the electrons between atoms that are bonded together covalently, property of the bond
54
what happens to covalent bond between two atoms that are the same
the electrons in the bond must be shared equally betwee the atoms as both atoms have the same electronegativity and the bond is completely non-polar
55
what happens to covalenet bonds between two atoms that are different
the electrons in the bond will not be shared equally between the atoms
56
polar bonds
covalent bonds where the electrons are attracted to the more electronegative atom
57
what are atoms in molecules and giant structues held togethe by
strong covalent, ionic, or metallic bonds
58
what attracts molecules and seperate atoms to one another
weaker forces called intermolecular forces
59
what are the three types of intermolecular forces
van der waals forces
dipole-dipole
hydrogen bonding
60
van der walls forces
acts between all atoms and molecules
61
dipole- dipole forces
acts only between certain types of molecules
62
hydrogen bonding
acts only between certain types of molecules
63
what may molecules with polar bonds have
a dipole moment
64
what happens in molecules with more than one polar bond
the effects of each bond may cancel leaving a molecule with no dipole moment.
they may also add up and so reinforce eachother depending on the shape of the molecule
65
where do dipole-dipole forces act
betwen molecules that have permanent dipoles
66
what will happen to two molecules with dipoles
they will attract one another
the molecules with dipoles will flip to give an arrangement were the two molecules attract
67
what are all atoms and molecules made up of
positive and negative charges even though they are neutral overall.
68
what are van der waals forces
the week electrostatic attractions between all atoms and molecules
69
what are van der waals forces in addition to
any other intermolecular forces
70
how does the size of van der waals react to number of electrons
increases with the number of electrons which means that atoms or molecules with larger atomic or molecular masses produce stronger van der waals forces than atoms or molecules with small atomic or molecular masses
71
what does van der waals forces explain
why the boiling points of noble gases increase as the atomic numbers of the noble gases increase
why the boiling points of hydrocarbons increase with increased chain length
72
what is hydroge bonding
a special type of intermolecular force with some characteristics of dipole-dipole attraction and some of a covalent bond
73
what does hydrogen bonding consist of
a hydrogen atom ' sandwiched' between two very electronegative atoms
74
what conditions have to be present for hydrogen bonding to occur
a very electronegative atom present with a lone pair of electrons covalently bonded to the hydrogen atom (eg water molecules)
75
why is intermolecular bonding strong in water
the oxygen atoms have lone pairs of electrons
the hydrogen atoms are highly elecron deficient because oxygen is very elecrtonegative and attract the shared electrons in the bonds towards it
76
what are hydrogne bonds represent by
dashes
77
what must there be for a hydrogen bond to occur
a hydrogen bond that is bonded to a very electronegative atom, this will produce a strong partial positive charge on the hydrogen
a very electronegative atom with a lone pair of electrons which will be attracted to the partially charged hydrogen atom in another molecule and form the bond
78
what are the only atoms electronegative enough to form a hydroge bond
oxygen, nitrogen, fluorine
79
hydorgen bond effect on boiling point
increases as these stronger intermolecular forces make the molecules more difficult to seperate
80
what happens to the hydrogen bonds in water when its in its liquid state
the hydrogen bond break and reform as the molecules are mvoing about
81
what happens to the hydrogen bonds when water freees
the water molecules are no longer free to move about and the hydrogen bonds hold the molecules in fixed positions resulting in a three dimensional structure resembling the structure of diamond
82
electron pair repulsion theory
each pair of electrons around an atom will repel all other electron pairs
the pair of electrons will therefore take up positions as far apart as possible to minimise repulsion
83
two kinds of electron pairs
shared pair or lone pair
84
what does the shape of a simple molecule depend on
the number of pairs of electrons that surround the central atom
85
two pairs of electrons
the molecule will be linear
the furthest awau from each other the two pairs can get is 180 degrees apart
86
three pairs of electrons
the molecule is called a trigonal planar
120 degrees apartf
87
four pairs of electrons
the molecule is called a tetrahedron
electron pairs are 109.5 degrees apart
88
five pairs of electrons
shape is trigonal bipyramid
89
six pairs of electrons
shape is octahedral
bond angles of 90 degrees
90
what do some molecules have
lone pairs of electrons
91
what do lone pairs affect
the shape of the molecule
92
what is the rule of thumb with lone pairs for shapes of molecules
2 degrees per lone pair
93
matter
anything with mass
94
arrangement of particles in a solid
regular
seen as crystal shapes have straight edges. solids have definite shapes
95
arrangement of particles in a liquid
random
seen as liquid changes shape to fill the bottom of its container
96
arrangement of particles in a gas
random
seen as a gas will fill its container
97
spacing in solid
close
solids are not easily compressed
98
spacing in liquid
close
liquids are not easily compressed
99
spacing in gas
far apart
gases are easily compressed
100
movement in solids
vibrating around a point
diffusion is very slow solids expand on heating
101
movement in liquids
rapid jostling
diffusion is slow. liquids evaporate
102
movement in gases
rapid
diffusion is rapid, gases exert pressure
103
energy changes heating a solid
when you first heat a solid and supply energy to particles it makes them vibrate more about a fixed position. this slightly increases the average distance between the particle and so the solid expands
104
energy changes turning a solid to a liquid
energy is needed to weaken the forces that act between the particles, holding them together in a solid state. temperature does not change as solid is melting because the heat energy provided is absorbed as the forces between particles are weakened
105
enthalpy
the heath change measured under constant pressure
106
heating a liquid
you supply energy to the particles which makes them move more quickly, they have more kinetic energy so the particles move further apart so liquids also expand on heating
107
turning a liquid to gas
you need to supply enough energy to break all the intermolecular forces between the particles.
108
heating a gas
as you heat a gas the particles gain kintetic energy and move faster. they get much further apart and so gases expand a great deal on heating
109
crystals
solids
regular arrangement held together by forces of attraction
110
what are crystals held together by
could be strong bonds or weak intermolecular forcesw
111
what does the strength of the forces of attraction affect
the physical properties of the crustal
112
what do ionic compounds have
strong electrostatic attractions betwee oppositely charged ions
113
why do ionic compounds have high melting points
as a result of the strong electrostatic attractions which extend throughout the structure. these require alot of energy to break in order for the ions to move apart from eachother
114
molecular crystals
consist of molecules held in a regular array by intermolecular forces. covalent bonds within the molceules hold the atoms together but they do not act between the molecules
115
proporties of molecular crystals
-soft and break easily
- low melting point
-does nit conduct electricity
116
macromoleuclar crystals
covalent bonds extend throughout the compound and have the typical proporties of a giant structure
117
diamond and graphite
both made up of carbon only
polymorphs or allotropes of carbon
different materials because their atoms are differently bonded ad arranged
118
diamond
consists of pure carbon with covalant bonding between every carbon atom, bonds spread throughout the structure
each carbon atom forms four single covalent bonds with other carbon atoms
forms a giant three dimensional lattice making it
- very hard
high melting point
does not conduct electricity because there are no free charged particles to carry charge
119
graphite
also consists of pure carbon but atoms are bonded differently from diamond
two tupes of bonding
- covalent
-van der waals forces
each carbon atom forms three covalent bonds to other carbon atoms
provides a two dimensional layer of linked hexagons of carbon atoms
delocalised electrons between layers
- soft material
high melting point (breaks down before it melts
- conducts electricity as it contains free electrons
