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inorganic > atomic orbitals (pike) > Flashcards

atomic orbitals (pike) Flashcards

1
Q

what are the charges of protons electrons and neutrons

A

proton = 1.6910^-19 faradays constant
electron =-1.6910^-19
neutron = 0

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2
Q

what are the relative charges of protons electrons and neutrons

A

proton = +1
electron = -1
neutrons = 0

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3
Q

what are the relative masses of protons electrons and neutrons

A

protons = 1837
electrons = 1
neutrons = 1837

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4
Q

what 2 numbers are atoms characterized by and what do they mean

A

atomic number Z - number of protons
mass number N - number of neutrons and protons

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5
Q

define isotopes, atomic mass and allotropes

A

Isotopes - atoms of the same element with a different number of neutrons
Atomic mass (A) - weighted average mass number of all isotopes present
Allotropes - different structural forms of a bulk element due to different spatial arrangement

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6
Q

outline the timeline and development of the atom

A

1808 - Dalton atom are indivisible
1904 - Thomson electrons surrounded by a soup of positive charge ( plum pudding model)
1911 - Rutherford atoms consisting of electrons moving around a nucleus
1913 - Bohr electrons around the nucleus but only certain energies allowed
post 1930 - Heisenberg orbitals

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7
Q

how do we prove the structure on atoms

A

One of the best ways of proving the structure of proving the structure of atom is through the interactions with electromagnetic radiation and it is described by its wavelength and frequency

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8
Q

what did louis de Broglie propose

A

Louis de Broglie proposed that if electromagnetic radiation could exhibit the properties of waves and particles, so could electrons (and every moving particle) also known as wave-particle duality

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9
Q

what is the Heisenberg uncertainty principle

A

it is not possible to determine the position and momentum of an electron at any particular instant in time

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10
Q

since we cannot determine the exact position and velocity of electrons what do we do instead

A

calculate the probability of finding an electron in a particular place

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11
Q

what is a node

A

points where displacement from center is zero

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12
Q

what is a boundary condition

A

requirement of a wavefunction to have a certain value at a certain point.
quantisation is due to the ends of the strings being fixed

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13
Q

what is the equation for the speed of light

A

speed of light = wavelength * frequency
speed of light 3*10^8 m/s

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14
Q

define wavelength

A

the distance between two peaks or two troughs of a wave

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15
Q

describe what happens when behaviors of electromagnetic radiation has properties of a wave

A

it will have a wavelength and a frequency, and when it goes through a small gap you will get diffraction patterns when you get constructive and destructive interference when two waves get wide

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16
Q

describe what happens when behaviors of electromagnetic radiation has properties of a particle

A

it has to have a certain mass and it has to have a certain energy and has to have discrete amount of it called quanta (quantisation). particle is a specific amount of energy of one kind of electron

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17
Q

what is the equation for energy of a particle

A

energy = planks constantfrequency planks constant = 6.2610^-34

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18
Q

describe Bohrs model of the atoms

A

Bohr introduced the idea of quantisation , and said that the electrons move around the nucleus in orbitals at a fixed distance. each orbit has a fixed radius, is given a quantum number and has a certain energy. the energy of an electro is based upon its quantum number

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19
Q

what happens when an electron moves down to a lower energy level

A

the excess of energy is emitted as a quantum of light, the change in energy is the change of the quantum of light

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20
Q

why does Bohrs model of quantisation only work for hydrogen

A

hydrogen only has one electron, when you have more than one electron, with other elements the electrons are going to repel so they are interacting with each other and not just the nucleus

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21
Q

what is the equation for momentum

A

p=mv
momentum = mass*velocity

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22
Q

how do you measure the position of an electron

A

needs to interact with a photon, due to the small size of electrons, suitable electromagnetic radiation will be very energetic. photons also have particle - like properties and will change the momentum of electrons

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23
Q

what is an orbital

A
  • Orbitals describe the electron density (probability for finding an electron) in space
    cloud of probabilities
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24
Q

what is a wave function

A

The mathematical function used to calculate the shape of atomic orbitals is called a wavefunction. wavefunctions are a mathematical functions of a position in space and has a single value at each position

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25
Q

what is the fundamental vibration

A

if a guitar string at both ends the simplest vibrations of the string is the fundamental vibration

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26
Q

for the fundamental vibration what is the wavelength

A

2L

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27
Q

what is the first harmonic

A

the first harmonic contains one further stationary point to the fundamental vibration. it consists of two lobes with opposite phases through the vibration + and -

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28
Q

what is the wavelength of the first harmonic

A

2L/2

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29
Q

what is the second harmonic

A

the second harmonic contains 2 nodes there are 3 lobes with alternating signs

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30
Q

what is the wavelength of the second harmonic

A

2L/3

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31
Q

what does solving the schrodinger equation give us

A

solving the schrodingers equation produces many wavefuctions (electrons can occupy different atomic orbitals if they have enough energy). the equation can only be solved exactly for two body systems, approximations are being used for atoms containing more electrons

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32
Q

why is the value of the wavefunction^2 important

A

the value of wavefunction^2 at each point in space is proportional to the probability of finding a particle

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33
Q

assumptions about wavefunctions/probability

A

finite there is a 100% chance of finding an electron in the atom
single valued- there can only be 2 probability of finding an electron at a certain point
continuous

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34
Q

why do we use hydrogen as a model

A

the hydrogen atom is the simplest. it only has one electron and only experiences one force which is attraction to the nucleus.
schrodingers equation can be solved exactly 2 body system

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35
Q

what is a radial system coordinate

A

how far is the position from the nucleus regardless of direction

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36
Q

what are the two angular components used to define

A

the directionand magnitude and both are conserved

37
Q

what is the radial boundary condition

A

about the distance to the nucleus r
if an electron belongs to the atom most of its density will be close to the nucleus. The wavefunction has a value the approaches to zero as the distance from the nucleus r increases
exponential decay

38
Q

how many boundary conditions do we expect for atoms

A

3D structure so 3 boundary condition

39
Q

what is the mathematical function of all atomic orbital expressed as

A

A*e^-Br
where A and B are kinds of constants
- does not depend on coordinates
- has different values for different orbitals
- have the same value everywhere in one orbital
- at large values of r the value of the function is very small so the electron lies close to the nucleus

40
Q

what is the angular boundary condition

A

refers to the direction specified by the two angles and the fact that an atom is spherical.

41
Q

what does the higher number of nodes mean

A

the higher the energy
the solution with the lowest energy - ground state
the solution with higher energies - excited states

42
Q

what does a radial node determine

A

effective size

43
Q

what do angular nodes determine

A

their shape

44
Q

what are the 3 quantum numbers

A

quantum numbers describe the size and shape of an orbital
1) n - principle quantum number
2) l - angular momentum quantum number/ subsidiary number
3) ml - magnetic quantum number
all whole numbers

45
Q

what does the principle quantum number tell us

A

n specifies the total number of nodes (angular and radial) in an orbital and gives an indication of the size and energy of the orbital

46
Q

how are the total number of nodes calculated

A

total number of nodes = n-1

47
Q

what does the angular momentum quantum number tell us

A

specifies the number of angular nodes in an orbital and describes the shape of the orbital

48
Q

what is the value of l between

A

l has an integer value between 0 and n-1
if n=4 l can be 0,1,2 or 3
because there cannot be a higher number of angular nodes then total nodes there is a restriction to the value of l

49
Q

what does the magnetic quantum number tell us

A

the ml counts the number of different orbitals that have the same values of n and l and describes the orientation of the orbitals

50
Q

what is the range of values for ml

A

ml can have any positive or negative integer between +l and -l
if l=1 ml = -1,0,1

51
Q

what do the different values of ml represent

A

represent different orientations of the same shape and energy and are related to the magnetic properties

52
Q

what is the equation for wavefunction for atomic orbitals

A

wavefunction = Aangularradial*exponential decay

53
Q

what is A in the wavefunction equation

A

A is the normalisation constant, used to put all the orbitals on the same scale.
the value of the constant is different for each orbital

54
Q

what is the exponential decay in the wavefunction equation

A

represents the dependence of the wavefunction from the distance to the nucleus
- creates the node at infinity common for all orbitals
- ensures that electrons belong to this atom
makes the value of the wavefunction decrease towards zero when increasing the distance from the nucleus

55
Q

for the wavefunction equation what happens if either the angular or radial part is missing

A

use the value of 1

56
Q

if the equation = 0 what does that tell us

A

nodes occur when the equation is equal to zero, if any of the terms is equal to 0 the overall function is 0
there are radial nodes when the radial part =0 and there are angular nodes when the angular part = 0

57
Q

how do we know the number of angular nodes

A

l= angular nodes

58
Q

how do we calculate the number of radial nodes

A

n-1-l

59
Q

compare the 1s and 2s and 3s orbitals

A

s orbitals are spherically symmetrical ans have no direction dependence
do not have angular nodes
1s does not have a radial nodes either
2s has one radial node the radial part is expressed at c-r
3s has 2 radial nodes expressed by a polynomical equation two solutions c-dr+r^2

60
Q

what is the electron density of s orbitals

A

For an s orbital, the electron density is highest near the nucleus and decreases smoothly as the distance from the nucleus increases. The probability density reaches zero at infinity, indicating that there is a finite probability of finding the electron at any distance from the nucleus within the orbital’s defined boundary
electron density is also proportional to the number of points at which the electron can be at a particular value of r
the number of points is proportional to the surface of a sphere of radius r=4pier^2

61
Q

how does the radial probability function change for 1s,2s and 3s

A

increase in size with n
the outermost lobe contains most of the electron density
the electron density is smaller for lobes with a smaller radii
the electron density at the nucleus is very small but not 0

62
Q

for multi electron atoms what does orbital energy depend on

A

the orbital energy depends on the quantum numbers n and l not ml

63
Q

what does the orbital energies depend on for a hydrogen atom

A

orbital energies depend only on n

64
Q

for hydrogen if the orbital energy is n what does that mean

A

2s and 2p are degenerate
3s,3p and 3d are also degenerate

65
Q

what is absorption

A

absorption promotes an electron from a lower to an upper energy level

66
Q

what is emission

A

emission allows an electron to decay from an upper to a lower level

67
Q

what does orthogonality mean

A

they cannot be written as a combination of any others

68
Q

how can we tell if two wave functions are orthogonal

A

two wavefunctions are orthogonal if their overlap integral is zero
the overlap integral means that the values of 2 wavefunctions are multiplied at each point and all these values are added up

69
Q

how does angular nodes cause orthogonality

A

orthogonality is caused by the relative psoitions of the nodes in the different orbitals
for angular nodes the node is a perfect reflection plane of symmetry

70
Q

how do radial nodes cause orthogonality

A
  • positive and negative results can be obtained when multiplying the points of 1s by 2s
  • when the overlapped positive and negative regions are added together they cancel each other exactly
71
Q

what is aufbau principle

A

the ground state electron configuration of an atom is found by putting each electron in turn into the available lowest energy

72
Q

what is hunds rule of maxiumum capacity

A

the ground state electron configuration of an atom is the arrangement with the maximum number of spin parallel electrons

73
Q

what is pauli exclusion principle

A

every electron must have a unique set of quantum numbers
an orbital cannot contain more than 2 electrons and these must be spin paired to have different ms values

74
Q

what is spin quantum number ms

A

related to the intrinsic magnetic moment of an electron
the spin can have 2 possible values + or - 0.5

75
Q

what is the electrostatic effect on orbital energy for many electron atoms

A

2s and 2p have different energy
electrons feel electrostatic attraction to the nucleus and repulsion from other electrons
the overall electrostatic effect is that the net attraction to the nucleus is reduced
each electron is partially shielded by other electrons from the full nuclear charge

76
Q

what is effective nuclear charge

A

in many electron atoms the nuclear charge than an electron experiences is lower than the true nuclear charge (z)

77
Q

what is the equation for effective nuclear charge

A

effective nuclear charge = nuclear charge - shielding
z* = Z-shielding

78
Q

what happens as the number of electrons increase in terms of Z and Z*

A

the nuclear charge increases and so foes the effective nuclear charge

79
Q

what is the equation for the energy of an orbital using Z*

A

e = -1313(Z*)^2/n^2

80
Q

define penetration

A

orbitals overlapping to some extent

81
Q

what effect does penetration have

A

increases the nuclear attraction for a 2s electron over than of 2p
decreases the shielding of 2s electrons by 1s electrons
the effective nuclear charge of a 2s would be greater than 2p so 2s are more stable

82
Q

what are the contributions to the total shielding for slaters rule

A

0 from all electrons in groups to the right
0.35 from each of the electrons in the same group 0.3 for 1s
0.85 from each electron in the n-1 shell
1 from each electron in lower shells

83
Q

what is the effects of Z* on atomic radii

A

from one element to the next, Z increases by 1 but shielding increases by only 0.35. so Z* increases by 0.65 overall the attraction increases making orbital small

84
Q

what are the valence electrons and what are the shielding effects

A

those in the outer highest energy quantum level
experiences more shielding than any other electron
generally have the highest value of n
they are responsible for the chemical properties of the atom and are involved in chemical bonding

85
Q

what are the core electrons and what are the shielding effects

A

all those in the inner quantum levels
are poorly shielded and experiences a high effective nuclear charge
have lower values of n
unable to take part in chemical properties of chemical bonding
they are important because acts as a shield for the valence electrons

86
Q

define ionisation energy

A

energy required to remove the highest energy electron from the atom in the gas phase to produce a cation

87
Q

what effect does removal of an electron have on shielding

A

removal of an electron also decreases shielding effects on other electrons so the energies of other electrons change

88
Q

describe the overall trends going down a group

A

valence electrons are very well shielded by core electrons
small decrease in ionisation energy down the group
significant increase in atom size
similar physical and chemical properties but not identical

89
Q

describe the overall trends going across a period

A

electrons from the same sub-shell dont shield very well so Z* increases rapidly
large increase in ionisation energy across the row
significant decrease in atom size

inorganic (12 decks)

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