1 atomic structure Flashcards
which letter is used to represent the atomic number?
Z
what does the atomic number tell us about an element?
the number of protons
what letter represents the mass number?
A
how do you calculate the mass number?
number of protons + number of neutrons
what is a positive ion called?
cation
what is a negative ion called?
anion
define isotope
isotopes are atoms with the same number of protons but a different number of neutrons
do isotopes have the same chemical properties?
yes
why do isotopes have the same chemical properties?
same number of electrons/same electron configuration
define ionisation energy
the amount of energy needed to remove a mole of electrons from a mole of atoms in the gaseous state
what is the first ionisation energy of potassium?
K(g) -> K+(g) + e-
why are second ionisation energies of some elements higher than the first?
the ion already has a positive charge
what shape is an s orbital?
spherical
what shape is a p orbital?
dumbbell
what is an orbital?
region within an atom that can hold up to two electrons with opposite spins
where do we find orbitals?
in each subshell within each shell
how many electrons does an s sub shell hold?
2
how many electrons does a p sub shell hold?
6
how many electrons does a d sub shell hold?
10
what would be the relationship between 2 electrons in the same orbital in terms of their spin?
have opposite spin as they repel eachother because both are negative
what are the two types of ionisation for a mass spectrometer?
electron impact and electrospray
describe electron impact
- sample is vaporised and high energy electrons are fired at it from an electron gun
- this knocks off one electron from each particle forming a 1+ ion
describe electrospray ionisation
- sample dissolved in a volatile solvent and injected through hypodermic needle to give a fine mist
- tip of needle attached to positive terminal of a high voltage power supply
- particles gain a proton
what does the mass spectrometer measure?
- relative abundance
- mass/charge ratio
give the 6 steps of TOF mass spectrometer
- vacuum
- ionisation
- acceleration
- ion drift
- detection
- data analysis
describe the vacuum stage of TOF
the entire machine is a vacuum inside to prevent any of the particles colliding with air molecules
describe ionisation for TOF
two methods where the sample particle gain a positive charge
describe acceleration in TOF
the positive ions are attracted to a negatively charged plate (amount they accelerate depends on m/z ratio) once accelerated all ions have same kinetic energy
describe ion drift in TOF
some of the ions pass through a hole in negatively charged plate and form a beam of particles that drift apart because they’re all travelling at different speeds
describe detection for TOF
different ions arrive at detector at different times. TOF is recorded and as each ion hits the detector it gains and electron which generates a current
why are the sample particles ionised in TOF?
so they can be accelerated towards plate and so they generate a current when hitting the detector
what is the trend in ionisation energy across period 3?
- general increase because across period 3 there is a greater nuclear charge
- so same amount of shielding so a greater attraction between nucleus and outer electron
how does the ionisation energy change down a group?
atomic radius increases so more shielding and weaker attraction from nucleus to electrons in outer shell.
ionisation energy decreases down the group
