topic two/twelve Flashcards
what are nucleons
particles in the nucleus of an atom
relative mass and charge of the subatomic particles
what is the atomic number
the number of protons
the mass number or nucelon number is
the number of protons + number of neutrons
notation for the atomic number
Z
notation for the mass number
A
An atom of any element contains equal numbers of which of the following sub-atomic particles?
electrons and protons
how many neutrons does H have
0.
it can have then 1 or 2
many isotopes are radioactive and can be used in
radiotherapy to treat like cancer with ionising radiation
why do isotopes have the exact same chemical reactions
they have the saem number of electrons.
why do isotopes have different physical properties
they have mroe neutrons and so more mass
what is the mass spectrometer used for
to determine the realtive atomic masses of elements. it can also be used to determine the structure of organic compounds
how does a mass spectrometer work
The sample to be analysed is first vaporised to form a gas. Next, it is bombarded by high-energy electrons, producing positive ions, which are then accelerated in an electric field. Note that a mass spectrometer produces ions with a one positive (1+) charge. The positive ions are deflected in a magnetic field depending on their mass to charge ratio (m/z or m/e). Ions with a higher mass to charge ratio are deflected less in the magnetic field than ions with a lower mass to charge ratio. Finally, the positive ions reach the detector, where they produce a mass spectrum.
how to calculate relative atomic mass from isotope
he mass number of each isotope (the isotopic mass) is multiplied by its percentage abundance. The sum of the isotopic masses multiplied by their percentage abundances are added together and then divided by 100 to give the relative atomic mass of a single atom.
how are energy levels organised
The principal energy levels are assigned numbers (n, the principal quantum number), with n = 1 being closest to the nucleus and of lowest energy. The further the energy level is from the nucleus, the higher its number (n) and the higher its energy
what is the shape of an s orbital
sphere
what is the shape of a p orbital
dumbbell
the main energy levels are split into…
sub levels which are assigned a number and the letter s,p,d or f
what does an atomic orbital represent
a region of space where there is a high probability of finding an electron
what does the pauli exclusion prinicple state
two electrons cannot have the same quantum number. two electrons can only occupy the same atomic orbital if they have opposite spins.
what is heisenberg’s uncertainty principle
it is not possible to know, at the same time, the exact position and momentum of an electron
n=1
s 2
n=2
s 2
p 6
n=3
s 2
p 6
d 10
n=4
s 2
p 6
d 10
f 14
what is the aufbau principle
electrons fill atomic orbitals of lowest energy first
which sub level has the lowest energy
the 1s sub level
are s orbitals or p lower energy
s
what are degenerate orbitals
ones of equal energy
there is an overlap between the 3d and 4s sub levels
this means the 4s sub level is of lower energy and fills before the 3d sub level
condensed electron configurations
use the notation [Noble gas] to represent part of it.
chromium electron configuration
1s2 2s2 2p6 3s2 3p6 4s1 3d5 or
1s2 2s2 2p6 3s2 3p6 3d5 4s1
copper electron configuration
1s2 2s2 2p6 3s2 3p6 4s1 3d10 or 1s2 2s2 2p6 3s2 3p6 3d10 4s1
how are electron boxes used
hunds rule
electrons fill orbitals in the saem sub level singly before pairing up.
em spectrum
as frequency increases
wavelength decreases
energy increases alongside
frequency
Higher energy =
higher frequency = shorter wavelength.
Lower energy =
lower frequency = longer wavelength.
infrared
suns heat
Low energy, low frequency
visible region
7 different colours
UV region
dangerous for human skin
High energy, short wavelength
When white light passes through a prism, what is produced
a continuous spectrum
differneces between spectra
when electrons are excited
they jump to higher energy levels
when electrons emit energy
they deexcite and return to lower energy levels
when are absorption line spectra produced
when electrons absorb energy and trnasition to higher energy levels
when is a visible light emission line spectrum oroduced
when electrons traisition from higher energy levels to the second main energy levels
relationship between energy and rfrequency formula
E = hv
Electron transitions to the n = 1 energy level
UV
Electron transitions to the n = 2 energy level
visible light
Electron transitions to the n = 3 energy level
IR
Which of the following statements best describes the visible emission line spectrum of hydrogen?
A set of four lines that converge at high frequency
in emission spectra, the lines converge at
higher frequencies
what is the highest energy end of each series of spectral lines known as
the convergence limit of that series.
the energy of the convergence limit of the UV series corresponds to what
the enrgy absorbed when an electron transitions from the n=1 energy level to the n=infinity energy level
when do eleectrons no longer experience the electrostatic attraction from the nuelus
at n= infinity
when electrons are at n=infinity,
it can be considered as left the atom
E=hv units
E is energy in joules, h is Planck’s constant, 6.63 × 10−34 J s, and v is the frequency, in s−1
what is the ground state
The ionisation of a hydrogen atom in its ground state corresponds to the electron transition from n = 1 to n = ∞. At this point, the electron is no longer attracted to the nucleus and the atom has been ionised.
what is the first ionisation energy of an element
the energy required to remove one mole of electrons from one mole of gaseous atoms to produce one mole of gaseous 1+ ions.
why are ionisation energies always positive (endothermic)
energy must be added to overcome the electrostatic attraction between the nucleus and valence electrosn
what is second ionisation energy
If an additional mole of electrons is removed from one mole of gaseous 1+ ions
why should we expect the ionisation energies to increase progressively as we remove negatively charged electrons from increasingly positive ions
it results in a stronger electrostatic attraction between the nucleus and the remaining electrons.
