S1.2+S1.3 Flashcards
what is a mass spectrometer used for?
to determine an element’s relative atomic mass from its isotope composition
how does a mass spectrometer work?
by firing high energy electrons at a sample of an element to create unipositive ions, then sorted by size using electric and magnetic fields to produce a graph called a mass spectrum
what is EM radiation?
a form of energy that travels as a wave
what is the order of the EM spectrum?
radio, micro, IR, visible, UV, x-ray, gamma
what is the trend from radio to gamma?
increase in energy, increase in frequency, decrease in wavelength
what does the EM spectrum show?
shows all wavelengths of EM radiation as a continuous spectrum
what does a line spectrum show? give an eg
only shows particular wavelengths eg hydrogen emission spectrum
how does the hydrogen emission spectrum work?
by looking through a spectroscope aimed at a discharge tube
1) hydrogen exposed to electricity which causes promotion of electrons to a higher energy level
2) here electrons are unstable so return to a lower energy level releasing energy in the form of a photon of light
3) this light diffracts through the slit in the spectroscope separating into its individual frequencies and displaying a single line on the emission spectrum
in hydrogen, what does a fall to level 2 give off?
visible light=balmer series
in hydrogen, what does a fall to level 1 give off?
UV light=lyman series
what does electrons behaving in this way provide evidence for?
electrons can only have a fixed value of energy
what happens at higher energy levels to the lines?
the lines on the emission spectrum get closer(converge) and eventually merge to form a convergence limit which is that the energy of the electron at this point can have any value
what is the energy it takes to reach the convergence limit called?
ionisation energy-the energy it takes to remove an electron from the hydrogen atom
what are orbitals?
regions of space with a high probability of finding an electron
what does the aufbau principle state?
electrons fill orbitals from the lowest energy level first
what does Hund’s rule state?
electrons will partially fill all orbitals of a single energy level before fully filling any single orbital of a single energy level
what does Pauli’s exclusion principle state?
electrons within a single orbital must have opposite spins from one another
how many of each s, p, d, f orbitals are there?
s=1, p=3, d=5, f=7
exception for Cr
1s2 2s2 2p6 3s6 3p6 4s1 3d5
exception for Cu
1s2 2s2 2p6 3s2 3p6 4s1 3d10
what is ionisation energy?
energy required to remove 1 mole of electron from 1 mole of gaseous atoms and corresponds to the convergence limit of an emission spectrum
E=HV
energy, planck’s constant, frequency
what is nuclear charge?
cumulative total + charge in nucleus and directly linked to the no. of protons present
what is electrostatic attraction?
attractive force of the negative electrons to the positive nucleus since opposite charges attract
what is the shielding effect?
reduction of the electrostatic attraction between valence electrons and the nucleus due to the blocking by inner electrons
how does nuclear charge change across a period and down a group?
increases across a period and down a group
how does shielding change across a period and down a group?
increases down a group but stays the same across a period
why does IE change down a group?
decreases bc nuclear charge increases, no. of electrons increases so shielding effect increases, decrease in electrostatic attraction between nucleus and valence electrons so less energy needed to remove electron
why does IE change across a period?
increases, electrons are added to same shell so shielding is the same, but nuclear charge increases, electrostatic attraction between nucleus and valence electrons increases, so more energy needed to remove electron
why does sulphur have a lower ionisation energy than phosphorus?
sulphur has 4 electrons in the 3p orbitals so its IE removes an electron from a p orbital containing 2 electrons, this exhibits repulsion and makes it slightly easier to remove than the 3p electron that is removed in phosphorus
