Topic 2: Atomic Structure Flashcards
1
Q
Dalton’s Atomic Theory
A
- all matter is made up of tiny particles called atoms
- an element consists of atoms of a single type
- compounds are a combination of 2 or more types of atoms
- atoms can’t be created/destroyed in a chemical reaction, only rearranged
2
Q
actual and relative masses of protons/neutrons
A
relative mass: 1
actual mass: 1.673 x 10^-24
3
Q
actual and relative masses of electrons
A
relative mass: 1/2000
actual mass: (negligible mass)
4
Q
actual and relative charge of protons
A
relative charge: +1
actual charge: + 1.602 x 10^-15
5
Q
actual and relative charge of electrons
A
relative charge: -1
actual charge: - 1.602 x 10^-15
6
Q
isotope
A
- atoms of the same element with diff neutron no.
- identical chem properties but diff physical properties compared to other atoms of same element
- since mass differs, other physical properties (e.g. density) also differs
7
Q
radioactive isotope
A
- isotope with unstable nucleus
- emits certain radiations
8
Q
uses of radioactive isotopes
A
- radiocarbon dating: C-14 exists in a set ratio to C-12 in living organisms, and when it dies, the C-14 isotopes decay, altering the ratio
- radiotherapy: Co-60 is a powerful gamma emitter used to treat cancer
- medical tracer: I-131 releases gamma and beta radiation and can be used to detect if the thyroid is functioning correctly + treat thyroid cancer
9
Q
stages of mass spectrometer
A
- vaporisation
- ionisation
- acceleration
- deflection
- detection
10
Q
Mass Spectrometer: Vaporisation
A
- all particles passing through get converted to gaseous state
- high vacuum here so particles don’t collide with air
11
Q
Mass Spectrometer: Ionisation
A
- the gaseous atoms are bombarded with high-energy electrons
- to generate positively-charged species
e. g. X (g) + e- -> M+ (g) + 2e-
12
Q
Mass Spectrometer: Acceleration
A
- the ions are attracted to positively-charged plates
- thus they’re accelerated in the electric field
- so they all have the same KE
13
Q
Mass Spectrometer: Deflection
A
- the positive ions are deflected by an electromagnetic field
- degree of deflection depends on mass-to-charge ratio
- high deflection: low mass, high charge
14
Q
Mass Spectrometer: Detection
A
- the beam of ions passing through the detector plate is electrically detected
- species of a particular m:z ratio are identified
- results are called “mass spectrum”
15
Q
electromagnetic spectrum
A
a spectrum of wavelengths comprised of the types of electromagnetic radiation
16
Q
properties of electromagnetic radiation
A
- has electric and magnetic fields that oscillate perpendicularly to each other and to the direction of travel
- behaves like both a particle and like a wave
- velocity of EM waves = velocity of light
- can travel in a vacuum
17
Q
characteristics of red light
A
highest wavelength, lowest frequency
18
Q
characteristics of purple light
A
lowest wavelength, highest frequency
19
Q
trends in electromagnetic spectrum
A
as wavelength increases:
- quanta energy decreases
- frequency decreases
thus: shorter wavelength = higher frequency = higher energy
20
Q
procedure for absorption spectrum to be produced
A
- pass electromagnetic radiation (e.g. light) through a collection of cold gas
- atoms will absorb some radiation at a certain frequency
- the spectrometer will compare the transmitted radiation to initial radiation and produce the absorption spectrum
21
Q
observations in absorption spectrum
A
- continuous spectrum of colours
- with vertical black lines at seemingly random intervals
- lines indicate absence of transmitted radiation
22
Q
procedure for emission spectrum to be produced
A
- heat gas with electric sparks
2. observe the output through a spectrometer
23
Q
what’s observed in emission spectrum
A
- a black background with seemingly random vertical lines of colour (line spectrum)
- only contains emissions at particular wavelengths
- lines tend to converge at lower wavelengths (violet)
- follows colour spectrum placements
24
Q
explanation of emission spectra
A
- electrons get excited by the photon energy supplied
- go from ground state to excited state
- electrons can only exist at certain fixed energy levels
- when dropping back to ground state they emit energy
- this corresponds to a particular wavelength and shows up as a line on the emission spectrum
25
why does the line spectrum converge?
because energy levels themselves converge at higher levels
26
continuous spectrum
a spectrum in which there are no gaps, each region blends directly into the next
27
line spectrum
a representation of light appearing as a series of discrete coloured lines
28
isoelectronic species
elements/ions that have the same electronic config.
29
Heisenberg's Uncertainty Principle
it isn't possible to measure the position AND velocity of a microscopic particle with 100% certainty
30
reasoning behind Heisenberg's Uncertainty Principle
it's impossible to locate a microscopic body without disturbing its position/velocity
31
Pauli's Exclusion Principle
no 2 electrons in an atom can have the same values for all 4 quantum numbers
32
Hund's rule
- electron pairing will not occur in orbitals in the same subshell
- until all orbitals are filled with at least one electron
33
Schrodinger Model
- uses wave functions to describe electron behaviour
| - shape of atomic orbitals depend on energy of electrons
34
types of wave functions
- principal quantum no. (n)
- azimuthal no. (l)
- magnetic no. (m1)
- spin no. (ms)
35
principal quantum number
represented by "n"
- describes main energy level (aka shell) occupied by the electron
- the higher the value of n = the farther the electron from the nucleus = the higher the energy associated with the shell
36
azimuthal quantum number
```
represented by "l"
- describes the shape of the orbital (aka subshell)
- formula: 0 to (n-1)
n being principal quantum no
- s, p, d, f, etc.
```
37
magnetic quantum number
```
represented by (ml, l in subscript)
- describes the orientation of an orbital around the nucleus
- formula: -l to l
l being azimuthal/angular quantum no
e.g. the x or y in 2px or 2py
```
38
spin quantum number
represented by "ms" (m subscript s)
- describes the spin orientation of the electron
- value: either spin up or spin down (0.5 or -0.5)
39
first ionization energy
energy needed to remove 1 mol of e-s from the ground state of 1 mol of gaseous atoms
e.g. H (g) --> H+(g) + e-
40
from and to what energy levels do removed electrons move to during ionisation?
from n = 1 to n = infinite!
