Atomic structure

Question 1

what two forces act on an electron?

Answer 1

electrostatic (columbic) which is between 2 charged particles and gravitational force between masses

Question 2

explain the rotating system of a proton and an electron

Answer 2

the proton is 1836 times the mass of an electron (the electron is waaay smaller than the proton) hence the centre of mass would be closer to the centre of the proton (in the nucleus). in reality the electron will be orbiting around the proton and the proton orbiting around itself ( so it would be stationary)

Question 3

explain the Heisenberg uncertainty principle

Answer 3

this states that the position and the velocity for very small particles such as an electron cannot be determined simultaneously. If the position of the particle is located with high accuracy that means that uncertainty in measurement of the velocity will be high and vice versa

Question 4

why is it possible to locate large particles/objects but impossible to observe small particles such as the electron

Answer 4

in order to see an object light has to be reflected off the object. light travels as in tiny packets of energy called a photon. when a photon of light hits the object the momentum of the photon is not strong enough so it doesn’t cause a displacement so the light is reflected off the object toward the observers eyes and they can pinpoint the exact position of the object. however when a photon hits the electron because it is so small it gets displaced because it is disturbed by the momentum of the photon so the position of the electron at the point of impact and when the photon reaches the observers eyes is different and that is delta x

Question 5

true or false

the grater the mass of a orbiting body the greater the uncertainty

Answer 5

false
the mass of the orbiting body is inversely proportional to the uncertainty. so the greater the mass the smaller the uncertainty

Question 6

What factors aid in the uncertainty in position and velocity of an hydrogen atom

Answer 6

it’s small size - it is easily disturbed by the momentum of a photon because of it’s small size which cause a shift in position from the moment of impact and the time when the photon reaches the observers eyes. this shift cause a large uncertainty in the position

it’s wave like property- the electron acts like a wave, waves are never in one position, as the definition states its a disturbance in space, so it tend to spread out in space making it hard to determine its velocity and position

Question 7

what can we measure that does not depend on the position or velocity of an electron ?

Answer 7

energy

Question 8

true or false

particles exhibit wave properties

Answer 8

true, particles such as electrons can undergo inference and diffraction just like a light (wave).

Question 9

what needs to occur for a particle to exhibit wave like properties ?

Answer 9

the particle needs to be bounded to an area of space with dimensions that are comparable to the natural wavelength of the particle

Question 10

what was de Broglie’s take on wavelength ?

Answer 10

any particle travelling with a linear momentum should have a natural wavelength.

Question 11

What is the diameter of a hydrogen atom?

Answer 11

1 A or 10-10 m or 100pm

Question 12

what is constructive interference?

Answer 12

when two waves of an amplitude a are in phase they interfere constructively and form a bigger wave wave with an amplitude of 2a.

Question 13

what is destructive interference?

Answer 13

when two waves are out of phase the interfere destructively and the entire wave cancel out

Question 14

which experiment proved that electrons have wave like properties?

Answer 14

young’s double slit experiment
electron exhibits diffraction patterns which is a wave property just like light (which is a wave) when a source is shone through a pair of vertical slits. regions of high and low electron density are located.

Question 15

what is a wave function

Answer 15

a mathematical representation describing the motion of a wave. the wave function can be positive or negative

The wave function allows us to calculate the probability of an electron that is within a certain distance away from the nucleus

wave function can also define the electron in terms of its wave properties

Question 16

what is the wave function squared?

Answer 16

the intensity of the wave motion eg the brightness of light or the loudness of sound. the squared of a wave function is equal to the electron density.

Question 17

does an electron in the ground state exhibit wavelike properties?

Answer 17

yes and this can be described by a wave function

Question 18

how would you express the wavefunction of the electron in the ground state?

Answer 18

the atom is 3D and in that space the electron has 3 coordinates, x y and z therefore the wave function can be expressed as a function of x, y and z [ψ(x,y,z)]

Question 19

explain how the probability of locating an electron in some region of space is P =∫ψ2dx.dy.dz”

Answer 19

the probability of locating the electron is p = wavefunction squared (P =ψ2). The probability of locating a electron in a specific spot is P =ψ2.dx , this is near impossible so instead the probability of locating the electron in some region of space is determined P =∫ψ 2 dx.dy.dz

Question 20

what is another name for the Hamiltonian ?

Answer 20

the wave operator

Question 21

define the Hamiltonian

Answer 21

A series of mathematical operations for kinetic and potential energy to be performed on the wavefunction

Question 22

true or false

for specific state of the system eg. ground state the wave function is specific and unique

Answer 22

true

Question 23

what is the energy function E

Answer 23

E is the total or net energy of the system under investigation.
so for a ground state hydrogen atom E would represent the energy of the electron in the field of the proton.

Question 24

What does classical mechanics state about energy ?

Answer 24

it states that energy should be continuous

Question 25

What does wave mechanics state about energy?

Answer 25

predicts that there is a definite state of | minimum (and non-zero) energy of the hydrogen atom

Question 26

how do H atoms become excited ?

Answer 26

They become excited from by absorption of discrete amount of radiation energy which moves them to higher orbital

Question 27

what are nodes?

Answer 27

Regions where ψ = 0 are called nodes. Therefore, the probability of finding the electron at a node is zero, that is, no electron density.

Question 28

what are the quantum numbers?

Answer 28

the principal quantum number (n) the orbital angular momentum quantum number (l) the magnetic quantum number (ml) all these quantum number come from SWE and they give the address of the electron

Question 29

give information on the principal quantum number (n)

Answer 29

The principal quantum number gives an account of the amount of energy of electron in the atom n= ( number of nodes present + 1) n= 1,2,3... as n increases the electron has more energy to overcome the attractive forces of the nucleus

Question 30

give information on the orbital angular momentum quantum number(l)

Answer 30

l is the number of angular nodes present l has n possible values l= 0, 1,2,3...n-1

Question 31

give information on the magnetic quantum number (ml)

Answer 31

tell us how the orbital is position based on any arbitrary random direction in space (magnetic field) for every value l, ml = 2l+1

Question 32

spin quantum number (ms)

Answer 32

this gives the configuration of the electron in the orbital the ms is allowed to have values of +or- 1/2. for electrons to occupy the same orbital they muss be of opposite spins.

Question 33

the orbital energy of Hydrogen depend on what?

Answer 33

The orbital energy of hydrogen depends only on the value of n. orbitals which the value of n is the same are known as degenerate (they have the same energy) disregarding of the values of l and ml. 2s and 2p have the same energy

Question 34

how do subshells come about?

Answer 34

if a orbital has same value of n and different values of l then the belong to a different subshell. each subshell has 2l+1 orbitals.

Question 35

How do you separate the energy levels in hydrogen?

Answer 35

electric discharge is passed through hydrogen gas the molecules absorb energy and split into atoms the atoms absorb energy electrons move to a higher energy state then fall back to ground state releasing energy in the form of radiation(photons)

Question 36

true or false | electrons are moving through specific energy levels

Answer 36

true | when an atom absorb energy it cause the electron to move to a higher energy level

Question 37

true or false | Atoms absorb and emit large amount of energy and exist in large energy states

Answer 37

false | atoms absorb and emit discrete amount of energy and therefore exist in discrete energy states

Question 38

what are the n values for the Balmer series ?

Answer 38

n = 2,3,4,5,6

Question 39

which spectrum of light does the Balmer, Lyman and paschen correspond to?

Answer 39

visible, ultraviolet and infrared

Question 40

What is orbital approximation

Answer 40

an electron in a many electron atom will feel the effect of the average charge of the nucleus and and the other electrons present in the atom.

Question 41

true or false | all orbitals/wavefunctions are symmetrical about the nucleus

Answer 41

true

Question 42

How do you know that the electronic configuration of helium is (1s)2 ?

Answer 42

a helium atom consist of 2 electron e1 and e2 and a nucleus with a charge of 2+. if e1 was to remain stationary and e2 was allowed to move freely, it would create an electron cloud that is symmetrical to the nucleus. e1 one would now feel the net effect of the electron cloud and the charge on the nucleus. the same thing would happen if e2 was to remain stationary and e1 allowed to roam freely generating a charged cloud. this results in both electron having a wavefunction similar to that of the hydrogen atom. since the ground state of hydrogen is 1s then both electrons will have a 1s orbital resulting in (1s)2.

Question 43

what would the wave function of the helium atom

Answer 43

. ψHe = ψ1S ψ1S

Question 44

true or false | an orbital is subdivided into 3 spin orbitals

Answer 44

false | an orbital is subdivided into 2 spin orbital

Question 45

what is pauli's principle

Answer 45

this principle states that only one electron can occupy one spin orbital

Question 46

would the 3rd electron form the lithium atom go to the 2s or 2p orbital and why?

Answer 46

It would go to the 2s orbital because looking at the orbital diagrams in the 2s the electron would be closer to the nucleus which is more energetically favorable and hence more stable than that of the 2p

Question 47

what does penetrating power of a orbital mean?

Answer 47

Penetration describes the proximity of electrons in an orbital to the nucleus. Electrons which experience greater penetration experience less shielding and therefore experience a larger Effective Nuclear Charge (Zeff) but shield other electrons more effectively.

Question 48

true or false | the greater the penetration, the less shielding

Answer 48

true an s electron will have a greater penetration that a p electron of the same shell because of it's proximity to the nucleus. because of this it will have less shielding but it will be a means of shielding for the p electron. the combined effects of the penetration and the shielding of s electron is more stable than the p electron of the same shell

Question 49

state Hund's rule

Answer 49

Hund's rule states that electrons will fill each orbital once before a second electron with a opposite spin occupies it. this is because electron in different orbitals but parallel spin has the tendency to stay apart (more stable).

Question 50

what is a cartesian coordinate used for

Answer 50

It can be used to determine the location of a point in a 3d space of cartesian(or xyz) coordinate system. All 3 axes are perpendicular. where the axis interact is known as the origin (000)

Question 51

what are the 3 polar coordinates?

Answer 51

r,  and . | the position of a mass moving at a distance r from nucleus is located using the 3 polar coordinates r, theta and psi

Question 52

Explain each polar coordinates and the possible values

Answer 52

r, radius is the distance of of the mass from the nucleus and it has a range of 0-infinity. theta (colatitude is the angle between the vector of the displacement r and the vertical axes (z axis) and has a range of 0- pi. psi (azimuth) is the horizontal angle that is formed with the radius and the xz plane. it has the range of 0 to 2 pi

Question 53

what 2 parts can the wavefunction be separated in using the spherical polar coordinates

Answer 53

it can be expressed as a radial part (R) which is a function of r it can also be expressed as angular part (y) which is a function of 0 and o theta and psi n,l,m(r,,) = Rn,l(r).Yl,m(,)

Question 54

what does the radial part of the wavefunction tell you

Answer 54

it gives you information about the variation about the electron density with distance r from the nucleus

Question 55

what does the angular part of the wavefunction tell you

Answer 55

gives information on the 3d region of space in which the electron is located (shape and orientation of orbital)

Question 56

what quantum numbers specify the angular wavefunctions

Answer 56

the quantum numbers l and ml

Question 57

what is the magnitude of the angular momentum of electrons in the s,p and d orbitals

Answer 57

0, square root 2 and square root 6,

Question 58

what is the first ionization enthalpy of an atom

Answer 58

is defined as the energy that must be supplied to the atom in order to excite the most weakly held electron out of reach of the nucleus. first ionization enthalpy increases as you move across the period