Atomic structure Flashcards
topic 1
1
Q
mass of proton
A
1.673 x 10^-27
2
Q
mass of neutron
A
1.675 x 10^-27
3
Q
mass of electron
A
0.911 x 10^-30
4
Q
charge of proton
A
+1.602 x 10^-19
5
Q
charge of neutron
A
0
6
Q
charge of electron
A
-1.602 x10^-19
7
Q
relative mass of proton
A
1
8
Q
relative mass of neutron
A
1
9
Q
relative mass of electron
A
1/1840
10
Q
relative charge of proton
A
+1
11
Q
relative charge of neutron
A
0
12
Q
relative mass of electron
A
-1
13
Q
nucleons
A
protons and neutrons because they are found in the nucleus
14
Q
have the same relative mass
A
protons and neutrons
15
Q
have opposite charges
A
protons and electrons
16
Q
have no charge
A
neutrons
17
Q
are found outside the nucleus
A
electrons
18
Q
explain why we assume that there are the same number of protons and electrons in an atom
A
because the overall charge of an atom is neutral so there must be an equal amount of protons and electrons in order for the atoms to cancel out and be neutral
19
Q
Dalton
A
elements are composed of indivisible atoms, cannot be broken down
20
Q
becquerel
A
discovered radioactivity this showed that particles could come from inside the atom therefore the atom was not indivisible
21
Q
thompson
A
discovered the electron, he showed that electrons were negatively charged and electrons from all elements were the same suggested that electrons were located within the atom in circular arrays - plum pudding model
22
Q
rutherford
A
gold foil experiment- found that most of the mass and all of the positive charge of an atom was in a tiny central nucleus.
23
Q
three fundamental particles
A
protons
electrons
neutrons
24
Q
how are protons and neutrons held in the centre of an atom
A
strong nuclear force which is stronger than the electrostatic forces of attraction that hold electrons and protons together in an atom
25
proton number/ atomic number
the number of protons in the nucleus
26
what is the number of electrons equal to
number of protons
27
what does the number of electrons in the outer shell determine
the chemical properties of an element and what sort of element it is
28
what does the atomic number define
the chemical identity of an element
29
what do all atoms of the same element have in common
number of protons
30
mass number
total number of protons and neutrons in the nucleus
31
what are the nucleons responsible for
almost all the mass of an atom because an electron weighs virtually nothing
32
isotopes definition
atoms with the same number of protons but a different number of neutrons
33
how do isotopes react
they react chemically in the exact same way as they have the same electron configuration
34
what are the 3 isotopes of carbon
12,13,14
35
what happens when isotopes are unstable
the nucleus of the atom itself breaks down giving off bits of the nucleus or energetic rays. this is the cause of radioactivity
36
half life
the time taken for half of an atoms radioactivity to decay
37
what is carbon 14
a radioactive isotope
38
half-life of carbon 14
5730 years
39
how is carbon 14 produced
by cosmic ray activity in the atmosphere
40
what is carbon 14 used for
to date organic matter
41
what can radiocarbon dating do
find the age of carbon based material up to 60,000 years old, though it is most accurate for materials up to 2000 years old
42
what does all living matter do
take in and give out carbon in the form of food and carbon dioxide meaning the level of carbon 15 stays the same
43
what is the name of hydrogen-2
deuterium
44
what is the name of hydrogen-3
tritium
45
when was radiocarbon dating introduced
1949
46
bohr
put forward the idea that the atom consisted of a tiny positive nucleus orbited by negatively charged electrons
- electrons orbited in shells of fixed size and the movement of electrons from one shell to the next explained how atoms absorbed and gave out light
47
Schrödinger
worked out an equation that used the idea that electrons had some of the properties of waves as well as those of particles, led to quantum mechanics which can be used to predict the behaviour of sub atomic particles.
48
chadwick
discovered neutrons
49
gilbert lewis
- the inertness of the noble gases was related to their having full outer shells of electrons
- ions were formed by atoms losing or gaining electrons to attain full outer shells
-atoms could also bind by sharing electrons to form full outer shells
50
what are lewis' theories the basis of
modern ideas of chemical bonding and explaining the formulae of many simple compounds using the idea that atoms tend to gain the stable electronic structure of the nearest noble gas
51
how many electrons does each shell hold
1. 2
2. 8
3. 18
4. 32
52
what is the mass spectrometer used to determine
relative atomic masshow
53
are relative atomic masses measured
on a scale on which the mass of an atom of carbon-12 is defined as exactly 12.
54
relative atomic mass equation
At = average mass of 1 atom / 1/12th mass of 1 atom of carbon-12
55
relative molecular mass equation
average mass of a molecule / 1/12th mass of 1 atom of carbon-12
56
what does the mass spectrometer determine
the mass of seperate atoms or moleucles
57
what happens in a time of flight mass spectrometer
the substances in the sample are converted to positive ions, accelerated to high speeds and arrive at a detector
58
two types of ionisation
electrospray ionisation
electron impact
59
mass spectrometer - vacuum
the whole apparatus is kept under a high vacuum to prevent the ions that are produced colliding with molecules from the air
60
mass spectrometer - electron impact
- the sample is vaporised
- high energy electrons are fired at it from an electron gun
- this usually knocks off one electron from each particle forming a 1+ Ion
61
mass spectrometer - electrospray ionisation
- the sample is dissolved in a volatile solvent and forced through a fine hollow needle
- that is connected to the positive terminal of a high voltage supply
- this produces tiny positively charged droplets that have gained a proton from the solvent
- the solvent evaporates from the droplets in the vacuum
- the droplets get smaller and smaller until they may contain no more than a single positively charged ion.
62
mass spectrometer - ion drift
- the ions pass through a hole in the negatively charged plate forming a beam and travel along a tube called the flight tube to a detector
63
mass spectrometer - acceleration
the positive ions are attracted towards a negatively charged plate and accelerate towards it, the lighter ions and more highly charged ions achieve a higher speed
64
mass spectrometer - data analysis
the signal from the detector is passed to a computer which generates a mass spectrum
65
mass spectrometer - detection
when ions with the same charge arrive at the detector the lighter ones are first as they have higher velocities
- the flight times are recorded
- the positive ions pick up an electron form the detector
- which causes a current to flow
66
what does the peak height give
the relative abundance of each isotope
67
why are different isotopes detected separately
because they have different masses
68
high resolution mass spectrometry
can measure relative atomic masses up to 5 decimal places of an atomic mass unit
69
what does the horizontal scale give
the m/z which is numerically the same as the mass number A
70
how are mass spectrometers used in space
they are used to identify the elements in rock samples
71
low resolution mass spectrometry
done to one decimal point
72
what casues the ions to accelerate through the mass spectrometer
they are attracted by a negatively charged plate
73
explain why ions formed in a mass spectrometer have a positive charge
because they lose an electron in ionisation
74
which ions will arrive at the detector first
ions with the smallest m/z
75
what forms the ions into a beam
they pass through a series of holes or slits
75
how can electron shells be represented
in an energy level diagram
76
how are electrons arranged
in shells around the nucleus with increasing numbers of electrons as they get further from the nucleus
77
formula for energy level number of electrons
2n^2
78
what are the shells called
main energy levels
79
which sublevels does the 1st energy level have
S
80
what are the 4 sub levels
SPDF
81
what sublevels does the 2nd energy level have
SP
82
what sublevels does the 3rd energy level have
SPD
83
what sublevels does the 4th energy level have
SPDF
84
quantum theory
describes the atom mathematically, the solutions to this equation give the probability of the electron in a given volume of space, called an atomic orbital
85
what do different orbitals have
different energiees
86
atomic orbital
the volume in space an electron fills
87
how many electrons can an orbital hold
2 electrons
88
what do the shapes of orbitals represent
a volume in space in which there is a 95% probability of finding an electron and they influence the shape of molecules
89
s orbital holds
2 electrons
90
p orbitals hold
6 electrons as come in groups of 3
91
d orbitals hold
10 electrons as come in groups of 5
92
which orbital fills first 4s or 3d
4s
93
spin
two electrons in the same orbital must have opposite spin which is represented by arrows up or down to show the different directions of spin
94
the rules for allocating electrons to orbitals
- lowest energy levels are filled first
- orbitals fill singly before pairing because electrons repel each other
- no orbital can hold more then 2 electrons
95
shorthand
use the previous noble gas then the remaining electrons
96
ionisation energy
the energy required to remove a mole of electrons from a mole of atoms in a gaseous state
97
how much energy does the first electron need to be removed
the least as it is being removed from a neutral atom
98
how much energy does the second electron need to be removed
more energy then the first as it is being removed from a +1 ion
99
successive ionisation energies
3rd, 4th, etc ionisation energies of an atom
100
how can you find the group number of an element based on its ionisation energies
the number before a massive jump in ionisation energies is the group number
101
trend of IE across a period
generally increase because nuclear charge is increasing making it more difficult to lose an electron
102
group 3 deviation from trend
this is because the outer electron is in a different orbital which has a slightly higher energy therefore it needs less energy to remove
103
Group 6 IE deviation from trend
Repulsion between the two electrons in p orbital makes it easier to remove one of them
104
Trends in IE down a group
General decrease, because the outer electron is in a main level that gets further from the nucleus in each case
- nuclear charge increases
