2 atomic structure Flashcards
what is the smallest part of an element
an atom
if atoms are neutral they contain
equal numbers of protons and electrons
relative mass of a proton
1
relative mass of a neutron
1
relative mass of an electron
1/2000
relative charge of a proton
+1
relative charge of a neutron
0
relative charge of an electron
-1
mass number =
equal to the number of protons and neutrons in the nucelus
atomic number =
equal to the number of proton in the nucleus and to the number of electrons in the atom. defines the element
charge of an atom
atoms have no charge so it should be 0, but by losing or gaining electrons they can gain a positive or negative charge
isotopes
atoms that contain the same number of protons but different numbers of neutrons
isotope properties
chemical properties are related to number of electrons so isotopes of the same element have identical chemical properties. since their mass is different, the physical properties like density and boiling point are different
relative atomic mass calculation
isotope A and isotope B
(A abundance x A mass) + (B abundance x B mass)
—————————————————————————–
100
how else can masses be determined
using a mass spectrometer
how do mass spectrometers work
a vaporized sample is injected into the instrument. atoms of the element are bombarded with a steam of high energy electrons in the ionization chamber. in practice the instrument is set so that only ions with a single positive charge are formed. the resulting unipositive ions pass through holes in parallel plates under the influence of an electric field where they are accelerated. the ions are then deflected by an external magnetic field.
what does the amount of deflection in a mass spectrometer depend on
mass of the ion and its charge. the smaller the mass and higher the charge the greater the deflection. ions with a particular mass/charge ratio are then recorded on a detector which measures both the mass and the relative amounts of all the ions present.
three different forms of radiation
gamma
alpha
beta
gamma radiation
highly penetrating
alpha radiation
stopped by a few cm of air
beta radiation
stopped by a thin sheet of aliminium
uses of radiation
nuclear power generation, the sterilization of surgical instruments in hospitals, crime dtection, finding cracks and stresses in food.
which isotope is used for carbon dating
14
C
6
what isotope is used for radiotherapy
131
I
53
what isotope is used as a trcer in medicine for treating an diagnosing illness
125
I
53
trend in size of energy levels surrounding the nucelus
the energy gap between successive levels get increasingly smaller as the levels get further from the nucleus.
sublevels in level 1
1
sublevels in level 2
2
sublevels in level 3
3
sublevels in level 4
4
what is heisenbergs uncertainty principle
“you cannot determine the position and momentum of an electron at the same time”
what is the aufbau principle
“electrons enter the lowest available energy level”
what is pauli’s exclusion principle
“No two electrons can have the same four quantam numbers”, two electrons an go in each orbital, providing they are of opposite sign
what is hund’s rule of maximum multiplicity
“when in orbitals of equal energy, electrons will try to remain unparied.” placing two electrons in one orbital means that, as they are both negativlely charged, there will be some electrostatic repulsion between them. placing each electron in a separate orbital reduces the repulsion and the system is more stable.
what is an orbital
a region in space where one is likely to find an electron
how many electrons can orbitals hold
2 (with opposite spin! (pauli’s exclusion principle) )
orbital s
spherical
orbital p
dumb bell
orbital d
various
orbital f
various
orbital s occurance
one in every principal level
orbital p occurance
three in levels 2 upwards
orbital d occurance
five in levels from 3 upwards
orbital f occurance
seven in levels from 4 upwards
orbital definition
a 3D statistical shape showing where one is most likely to find an electron.
why are orbitals not filled in numerical order
because the principal levels get closer together as you get further from the nucleus. this results in overlap of sub levels. the first example occurs when the 4s orbital is filled before the 3d orbitals.
exceptions in electron configuration
copper and chromium
isoelectronic
has the same electronic configuration
what can EM waves travel through
space and depending on the wavelength, matter
c =
v x lambda
velcoity =
frequncy x wavelegnth
electromagnetic radiation is a form of
energy
how to find relative atomic mass of off a mass spectrum
read off the graph and then use figures normally
why is the x axis (mass/charge) nearly always just the mass
because the charge will be +1 from the chlorine ions
what is the x axis of the mass spectrum
mass/charge (or just mass)
what is the y axis of the mass spectrum
relative abundance
when are emission spectra produced
when photons are emitted from atoms as excited electrons return to a lower energy level
the line emission of hydrogen prrovides evidence for
the existence of electrons in discrete energy levels, which converge at higher energies.
where do the highest energy levels converge
at the ionisation energy
c (velocity) =
lamda (wavelength) x v (frequency)
what area of the EM spectrum is visible light
inbetween UV and IR
which has the highest energy with a short wavelength and high frequency
gamma waves
which has the lowest energy with longest wavelength and lowest frequency
radiowaves
E is proportional to
1/lamda
what is the visible emission spectrum due to
electrons falling into the n=2 level from higher enrgy levels
why do lines in the spectrum converge aat higher enrgy
as the energy levels get closer together as the value of n increases.
what colour is n=6 –> n=2 transition
violet
what colour is n=5 –> n=2 transition
blue
what colour is n=4 –> n=2 transition
blue-green
what colour is n=3 –> n=2 transition
red
what wavelength is a violet transition
410
what wavelenght is a blue transition
434
what wavelength is a blue-green transition
486
what wavelenght is a red transition
656
longest wavelength =
shortest f
what is odd about lines 5 and 6 and 7 and 8 in the visible region
they are considered UV but are above 400 so are not offically in the visible region. (but you can see them)
homogenous mixture
same composition throughout (uniform)
heterogenous mixture
different composition throughout (non-uniform)
compare the chemical properties of isotopes
generally the same
compare the physical properties of isotopes
generally the same
continous spectrum
radiation spread over all wavelengths or energies
line spectrum
radiation spectrum emitted at a certain wavelength or energy
max electrons in a s orbital
2
number of atomic orbitals in an s orbital
1
max elecrons in a p orbital
6
max electrons in a d orbital
10
max electrons in a f orbital
14
number of atomic orbitals in a p orbital
3
number of atomic orbitals in a d orbital
5
number of atomic orbitals in a f orbital
7
what is electronegativity
power to attract the 2 electrons in a covalent bond
2,3-dihydroxybutanedioc acid produces
2 H+ ions
superimposable
ability to place one object over ano9ther in such a way that both are visible clearly
enantiomers
nonsuperimposable mirror image structures
chiral centre
the carbon that is directly attached to four distinct groups
steroisomers
compounds differing only in spatial arrangement of atoms
achiral
mirror image can be super imposed with molecule
optically active
ability of a molecule to rotate plane polarized light known as optical activity. molecules that can do this are optically active
Plane-polarised light is
composed of waves that vibrate in only one plane
disteroisomers
two isomers which do not behave as mirror images
mass =
density x volume
volume =
moles x 24dm
moles =
conc x vol
acid dissosciation constant
quantitative measure of the strength of an acid in solution
delta energy =
h v
plancks constant x frequency
