Chapter 5: Electrons and bodning Flashcards
(114 cards)
1
Q
how many electrons are in shell 1?
A
2 electrons
2
Q
how many electrons are in shell 2?
A
8 electrons
3
Q
how many electrons are in shell 3?
A
18 electrons
4
Q
how many electrons are in shell 4?
A
32 electrons
5
Q
other name for shells:
A
energy levels
6
Q
what happens as shell number increases?
A
energy increases
7
Q
what is the principal quantum n?
A
the shell number or energy level number
8
Q
what is the wave nature of an electron?
A
electrons can only fit into energy levels around an atom
9
Q
formula for number of electrons:
A
2n^2
10
Q
what are shells made up of?
A
atomic orbitals
11
Q
what is an atomic orbital?
A
a regional around the nucleus that can hold up to two electrons with opposite spins
12
Q
description of an electron:
A
a negative charge cloud with the shape of the orbital (electric cloud)
13
Q
how many electrons can an orbital hold?
A
one or two electrons, no more than
14
Q
orbital names:
A
s p d f
- each orbital has a different shape
15
Q
shape of electron cloud in s orbital:
A
electron cloud has the shape of a sphere
- s orbital can hold one or two electrons
16
Q
what happens as the shell number increases in the s orbital?
A
the radius is greater of the s orbital
17
Q
shape of electron cloud in p orbital?
A
dumb bell shape
- orbital can contain one or two electrons
- there are separate p orbitals at right angles to one another (px, py, pz)
18
Q
how many electrons can one orbital of the p orbital contain?
A
2 electrons
19
Q
how many p orbitals are there
A
3 at right angles from each other
20
Q
names of p orbitals:
A
px, py, pz
21
Q
how many p orbitals does each shell from n = 2 contain?
A
contains three p orbitals
22
Q
what happens to the l orbitals when the shell number increases?
A
the greater the shell number, the further the p orbital is form the nucleus
23
Q
what does each shell from n = 3 contain?
A
5 d-orbitals
24
Q
what does each shell from n = 4 contain?
A
contains seven f-orbitals
25
which sub shells are present in the first shell?
1s
26
which sub shells are present in the second shell?
2s + 2p
27
which sub shells are present in the third shell?
3s + 3p + 3d
28
which sub shells are present in the fourth shell?
4s + 4p + 4d + 4f
29
number of electrons in shells 1,2,3,4:
2,8,18,32
30
why does each new shell gain?
each new shell gains a new type of orbital
s1 p3 d5 f7
31
how many electrons fit into each orbital?
2 electrons fit into each orbital so the number of electrons in each sub shell increases
s2 p6 d10 f14
32
do subshells have the same energy levels?
subshells in shells have slightly different energy levels
33
which subshells have a higher energy level?
within each shell, the new type of subshells added has a higher energy
e.g 2p is the new type + has higher energy than 2s
34
order of filling in n = 2
2s 2p
35
order of filling in n = 3
3s 3p 3d
36
order of filling in n = 4
4s 4p 4d 4f
37
what is 3d subshell energy higher than?
higher than energy level of 4s subshell
38
what fills before 3d subshell
4s subshell
39
how many orbitals can each orbital hold?
two electrons
40
what is the charge of electrons and what do they do?
negatively charged and repel each other
41
what is spin of electrons?
it is a property of electrons either up or down
42
what do arrows of electrons show?
spin either up or down
43
spin in an orbital:
two electrons in an orbital have opposite spins
44
what do opposite spins do?
help to counteract the repulsion between negative charges of two electrons
45
energy levels of orbitals within subshells:
within a subshell, orbitals have the same energy
46
what happens before pairing of electrons start?
one elecetron occupies each orbital before pairing
- this prevents repulsion between paired electrons until there is no further orbital available at the same energy level
47
what is the shorthand of 1s2 2s?
[He] 2s1
48
what is the shorthand for 1s2 2s2 2p6 3s1?
[Ne] 3s1
49
what is the shorthand of 1s2 2s2 2p6 3s2 3p6 4s1?
[Ar] 4s1
50
when are cations formed?
known as positive ions
- formed when atoms lose electrons
51
when are anions formed?
- known as negative ions
- formed when atoms gain electrons
52
what can the periodic table be divided into?
blocks which correspond to their highest energy sub shell
53
what is the s block?
the highest energy electrons in the s-subshell
54
what is the p block?
highest energy electrons inthe p-subshell
55
what is the d-block?
highest energy electrons i’m the d subshell
56
what happens to the subshells when forming ions?
the highest energy sub shells lose or gain electrons
57
sub shells in the d-block elements:
4s sub shell is at a lower energy than 3d subshell so is filled first + empties first
58
What is ionic bonding?
The electrostatic attraction between positive and negative ions, it holds together cations and anions in ionic compounds
59
common cations:
metal ions Na+, Ca2+, Al3+
ammonium ions NH4+
60
common anions:
non metal ions Cl- O2-
polyatomic ions NO3- SO42-
61
what do the simplest ionic compounds contain?
metal ions and non metal ions
62
transfer of outer shell electrons from a metal atom:
transferred to outer shell of a non metal atom
63
What is formed during electron transfer?
Positive and negative ions
64
Electron configuration of ions formed:
Ions formed often have outer shells with the same electron configuration as the nearest noble gas
65
In what direction do ions attract?
Each ion attracts oppositely charged ions in all directions.
66
Structure of ionic compounds:
When attracted, form giant ioni lattice structure + contain billions of ions
67
What is the number of ions in a compound dependent on?
The size of the crystal
68
What state are ionic compounds at room temp?
Most are solids
69
Why are ions solid at room temperatures?
There is an insufficient energy to over come the strong electrostatic forces of attraction between oppositely charged ions in the giant ionic lattice.
70
Why do ionic compounds have high melting and boilings points?
To provide large quantity of energy needed to overcome strong electrostatic attraction between the ions
71
Which ionic compounds have higher melting points?
Lattices containing ions with greater ionic charges as there is a stronger attraction between ions
72
What are ionic compound attraction dependent on?
size of ions
73
What do many ionic compounds dissolve in?
Polar solvent e.g water
74
What do polar molecules do to ionic compounds?
Polar water molecules break down the lattice and surround each ion in solution
75
when is an ionic compound less soluble?
in a compound made of ions with large charges the ionic attraction may be too strong
76
NaCl ions and solubility at 20°C:
Na+ and Cl-
6.1 mol dm-3
77
CaCl2 ions and solubility at 20°C:
Ca2+ and Cl-
0.67
78
Na2CO3 ions and solubility at 20°C:
Na+ and CO32-
2.0 mol dm-3
79
CaCO3 ions and solubility at 20°C:
Ca2+ and CO32-
1.3 x 10^ -4
80
What two processes does solubility require?
- The ionic lattice must be broken
- water molecules must attract and surround the ions
81
What does the solubility of an ionic compound depend on?
- relative strengths of attraction between ions and water molecules
- attractions in giant ionic lattice have the greater effect and solubility decreases as ionic charge increases.
82
Do ionic compounds conduct electricity ?
- does not conduct electricity in solid but does when melted or dissolved
83
ions and charge in a solid state:
- ions are in fixed position in giant ionic lattice
- there are no mobile charge carriers
- non conductor of electricity in solid state
84
ions when liquid is dissolved in water:
- solid ionic lattice breaks down and ions are free to move as mobile charge carriers
85
summary of properties of ionic compounds:
- high melting and boiling points
- tend to dissolve in polar solvents e.g water
- conduct electricity in liquid state / aqueous solution
86
covalent bond definition:
the strong electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms
87
in what atoms does covalent bonding occur?
- non metallic elements e,g H2 O2
- compounds of non metallic elements e.g H2O CO2
- polyatomic ions e.g NH4+
88
what happens during covalent bonding?
pairs of electrons are shared between two atoms
- atoms are bonded together in a single unit (a small molecule, a giant covalent structure, charged polyatomic ions)
89
atomic orbitals in covalent bonds:
atomic orbitals overlap + each contain one electron
90
What is the shared pair of electrons in covalent bonds attracted to?
The nuclei of both bonded atoms
91
Outer shells in covalent bonds:
Atoms often have outer shells with the same electron structure as the nearest noble gas
92
what is ‘localised’ in covalent bonding?
acts only between shared pair of electrons and the nuclei of two bonded atoms
- results can give a molecule
93
what is a molecule?
consists of two or more atoms e.g H2 H2O
- the smallest part of a covalent compound that can exist while retaining the chemical properties of the compound
94
what does a displayed formula show?
the relative positioning of atoms and bonds between them as lines
- paired electrons that are not shared (lone pairs) can be added to display formulae
95
what atoms are covalent bonds usually formed from?
- Carbon forms 4 bonds
- nitrogen forms 3 bonds
- oxygen forms 2 bonds
- hydrogen forms 1 bond.
96
Electron configuration of boron:
1s2 2s2 2p1
97
what does the electron configuration of boron show?
only three outer shell electrons can be paired
98
what compounds does boron form?
- covalent compounds
e.g boron trifluoride BF3
99
what does BF3 show?
predictions for binding cannot only be based on noble gas electron structure
100
electron structure of phosphorus:
[Ne] 3s2 3p3
101
florida formula for phosphorus
PF3, PF5
102
formula of fluoride for sulfur:
SF2, SF4, SF6
103
formula of fluoride for chlorine:
CIF, CIF3, CIF5, CIF7
104
electron configuration of sulfur:
[Ne] 3s2 3p4
105
electron configuration of chlorine:
[Ne] 3s2 3p5
106
what is expansion of the octet?
- when the outer shell contains more electrons than the nearest noble gas
107
when is expansion of the octet possible?
only possible from n = 3 when a d sub-shell becomes available for the expansion
108
when do multiple covalent bonds exist?
when two atoms share more than one pair of electrons
109
electrostatic attraction in double bond:
the electrostatic attraction is between two shared pairs of electrons and the nuclei of the bonding atoms
110
what is a triple covalent bond?
the electrostatic attraction between three shared pairs of electrons and the nuclei of the bonding atoms
111
what is a dative / coordinate bond?
a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only
- shared electron pair was originally a lone pair of electrons on one of the bonded atoms
- e.g NH3 + H+ ion → NH4+
112
what is a dative covalent bond shown by?
an arrow to show which atom provides both electrons to the covalent bond
113
why can’t you tell which is the dative covalent bond?
all bonds are equivalent
114
what does average bond enthalpy measure?
covalent bond strength
- the larger the value, the stronger the covalent bond
