Atomic Structure Flashcards
(19 cards)
which letter is used to represent the atomic number of an atom
Z
what does the atomic number tell us about an atom
atomic number = number of protons in an atom
what letter represents mass number
A
how is the mass number calculated
number of protons + number of electrons
define relative atomic mass
average mass of all isotopes of an element compared to 1/12 the mass of a carbon-12 atom
what is an isotopes of an elements
same element with different number of neutrons but same number of protons
how many orbitals and electrons do the shells contain
1s - 1 orbital , 2 e
2s- 1 orbital, 2 e
2p- 3 orbital, 6 e
3s- 1 orbital, 2 e
3p- 3 orbital, 6 e
4s- 1 orbital , 2 e
3d- 5 orbital, 10e
does 3d or 4s have a higher energy level
3d
what is an orbital
region around nucleus that can hold up to 2 electrons
explain why chromium does not fit the trend in electronic configuration
it only has one electron in 4s shell before filling 3d
what would be the relationship between 2 two electrons in the same orbital in terms of their spin
have opposite spin and both negative so they repel
explain why copper does not fit the trend in electronic configuration
it only has one electron in 4s shell before filling 3d
what are the 2 types of ionisation for a mass spectrometer
Electron impact: electron gun (hot wire filament with current through it emitting electrons) knocks off one electron from each particle to form 1+ MOLECULAR IONS (these ions fragment).
Electrospray: sample dissolved in volatile solvent (e.g. water or methanol) and injected through a fine hypodermic needle to give an aerosol. Needle attached to positive terminal of a high-voltage power supply and particles gain a proton from the solvent as they leave the needle, producing XH+ ions (+1 charge and mass of Mr + 1). (ions rarely fragment)
when would you use the different types of ionisation in a mass spec
Electron impact for organic or inorganic molecules with low formula mass
Electrospray used for substances with higher molecular mass including biological molecules
Describe how a TOF mass spectrometer works
Acceleration positive ions attracted towards a negatively charged plate.
lon Drift - ions pass through hole in plate, form a beam with constant kinetic energy, travel along tube to detector. Time of flight is therefore directly proportional to the square root of mass.
Detection - positive ions pick up electrons, current flows, m/z value and time of flight recorded. Largest current from most abundant ions
Define first ionisation energy
the energy needed to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous 1+ atoms
