Chapter 1 - Atomic Structure Flashcards
what is the relative mass and charge on a neutron
mass: 1
charge: 0
what is the relative mass and charge of a proton
mass: 1
charge: +1
what is the relative mass and charge of an electron
mass: 1/1840
charge: -1
define relative atomic mass
the average mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12.
what must initially happen to an atom or molecule before it is put into a mass spectrometer
it must be ionised
how can atoms or molecules be ionised
using an electron gun
or using electrospray ionisation
describe how the electron gun ionises atoms
en electron is shot at an atom in a high vacuum chamber
the electron knocks off an electron off the atom to form a positive ion
how is electrospray ionisation carried out
a high voltage is applied to a solution with dissolved biomolecules
the high voltage causes the solvent to become ionised and break into many small droplets which are small enough to be considered a gas
what conditions must be present for electron impact ionisation to be successful
there must be a high vacuum in the chamber
the atom must be in a gaseous state
pros of electron impact ionisation
it can be done on individual atoms
it is very powerful and effective
cons of electron impact ionisation
it’s powerful so it may cause fragmentation in biomolecules which may cause inaccuracy in the mass spectrometer reading
describe the method of mass spectroscopy
sample introduced at low pressure
electron gun or electrospray used to ionise sample
the sample becomes a positive ion
the ions are accelerated with a negatively charged plate, then focused into a beam using a magnetic field
the ions are deflected, the deflection depends on the mass to charge ratio of each ion
lightest ions are deflected the most
ions reach the detector where they gain an electron and produce a current which is detected
the size of the current is proportional to the abundance of each isotope
a mass spectrum can be produced which cab be used to calculate the Ar of the sample
what does m/z mean
mass to charge ratio
if two molecules of different mass are in one spectroscope, what about them is the same
the energy they are accelerated to is the same
the distance they travel is the same
the time taken to travel the distance is different
the mass is different (it is usually what you are finding)
what equation can be used to find the velocity of a particle in a mass spectrometer given its distance and time taken to travel said distance
velocity = distance/time
v=d/t
what equation can be used to find the mass of a sample when the velocity and energy are known
1/2mv² = KE
how many atomic orbitals are there
name them in order of energy
four
s, p, d, f
how many electrons can one orbital hold
2
how many electrons can the s orbital hold in total
2
how many electrons can the p orbital hold in total
6
how many electrons can the d orbital hold in total
10
how many electrons can the f orbital hold in total
14
What orbitals does the first shell contain
only 1s
What orbitals does the second shell contain
2s, 2p
.
.
What do blocks in the periodic table indicate
the last energy level of the atom
why must the ‘electrons’ in boxes have different pointing arrows
to show th at they have different directions in their spin
what are the three rules for filling orbitals
orbitals with lower energy are filled first
orbitals of the same energy fill singly before they pair up
only 2 elections to an orbital
define ionisation energy (word for word)
the energy required go remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
what is the unit of IE
kJ/mol
how does the IE change as electrons are removed and why
the energy needed becomes greater because as each electron is removed, the remaining ion becomes more positively charged
as the ion becomes more positive, the electrons experience more attraction to the nucleus
which required more energy to overcome
what is the equation for the first ionisation energy of sodium
Na(g) —> Na(g)^+ + -e^-
what s the second ionisation energy for sodium
Na^+(g) —-> Na^2+(g) + e^-
what factors affect ionisation energy
atomic radius
nuclear charge
electron shielding
how does the atomic radius affect IE
as the radius increaces, the IE decreaces
how does the nuclear charge affect the IE
the greater nuclear charge the more energy required
how does the electron shielding affect the IE
the more shells, the less energy required
define shielding in an atom
the number of shells in the atom
how does IE change as you go across periods
there is a general increace across a single period
but the IE drops dramatically at the start of a new period
how does the IE change from group 2 to 3 and why
group 3 requires less energy than group 3
in group 2 the outermost electron is in an s orbital, meanwile group 3 is in a p orbital
p orbitals have more energy than s orbitals so the electron needs less energy supplied to it to leave its arrangement
how does the IE change from group 5 to 6 and why
group 6 requires less energy than group 5
in group 5 the p orbital is filled singly, meanwhile in group 6 an one of the of the p orbitals is fully filled
the 2 electrons repel eachother in addition to the energy supplied
so less energy is needed to ionise a group 6 atom than a group 5 atom
what is hunds rule
within a sublevel, place one electron per orbital before pairing them
what is the pauli exclusion principle
each orobital can only hold up to two electrons with opposite spins
what is the equation to find a particles mass from its mass number
mass number = (mass of particle in kg / avogadros constant) × 1000
what equation can be used to find a particles energy from its mass, time, and distance travelled
2KE = m(d^2/t^2)
what equation can be used to find the mass or time of one isotope from the mass and time of another
m1/t1^2=m2/t2^2
what values do two particles share when they are measured using the same mass spectrometer
the energy and distance travelled
why do isotopes have the same reactivity
because they have the exact same electron arrangement
write an ionic equation to represent the ionisation of molecule X in spray ionisation
X + H^+ —–> XH^+
write an ionic equation to represent the ionisation of molecule X in electron bonbardment
X(g) + e- —–> X^+(g) + 2e^-
when a molecule is mass spectrometered, how can you find its mr using a mass spectrum
average of all (m/z - 1)