Atomic structure (P1) Flashcards
define relative atomic mass
the average mass of an atom of an element on a scale where the mass of an atom of carbon-12 is exactly 12
what are the 2 exceptions when it comes to electron configurations+draw them.
Atomic numbers: 24+29
Copper+chromium
Copper(29):1S2,2S2,2P6,3S2,3P6,4S1,3D10
Chromium(24): 1S2,2S2,2P6,3S2,3P6,4S1,3D5
define relative molecular mass
average mass of a molecule on a scale on which a mass of an atom of carbon-12 is eaxctly 12
define relative isotopic mass
the average mass of an atom of an isotope of an element on a scale which the mass of an atom of carbon-12 is exactly 12
what does the mass number consist of?
number of protons +neutrons in the nucleus of an atom
what does the atomic number consist of?
the number of protons and electrons
how do you work out the number of neutrons
mass number-proton number
what did john dalton propose about the atom(1800)
atoms are spheres and each element have different spheres
what did jj thompson discover?what was his model
the electron, plum pudding model. electrons in a positive pudding
what did rutherford discover after jj thompson? what did he propose about this subatomic particle and the rest of the atom?
discovered the nucleus-very small and positive. rest of the atom=empty in a negative cloud
how did Rutherford come to his conclusion about the nucleus?
gold leaf experiment. he shot positive alpha particles at gold. most went through, small no. deflected.-hitting the pos nucleus
what did niels bohr propose? why?
proposed fixed energy shells as rutherfords model of cloud of electrons would collapse into pos nucleus
what subshell fills up first and why?
4s-lower energy level
define ionisation energy.
the minimum amount of energy required to remove 1 mole of electrons from one mole of atoms in the gaseous state.
what is the difference between the formation of ions between transition metals and normal elements in the way that there electrons are removed?
transition metals remove electrons from 4s subshell whereas others remove from highest energy level (3d)
what is ionisation dependent on?(3)
-shielding
-atomic size
-nuclear charge
what is the ionistion energy trend down groups? why?
atomic radii increases as you go down the group, so attraction is weaker. there is more shielding as more shells=less energy required
what is the trend for ionisation energies across a period?
generally increases bc no of protons increases so attraction increases, shielding is similar but no effect
in period 3 what are the two exceptions in ionisation energies?
between magnesium and aluminum
and between phosphorus and sulfur
across period 3 why does the ionisation decrease between magnesium and aluminum when it should increase?
aluminiums outer electrons are in a higher energy level (3p) then magnesium(3s) therefore further away from the nucleus
across period 3 why does ionization decrease between phosphorus and sulfur when it should increase?
phosphorus and sulfur both ahve electrons in the 3p orbital so shielding is the same. ionisation energy decreases as in sulfur there is 4 electrons in the 3p so electrons repel each other whereas in phosphorus there is only 3 with no repulsion, so less energy is recquired to remove an electron from sulfur as it has exisiting repulsion
what are the 4 steps during mass spec?
- ionisation
- accelaration
- ion drift
- detection
what occurs during ionisation in mass spec?
atoms are turned into ions through electrospray ionization or electron impact
what occurs during electrospray ionisation
- sample dissolved in a solvent
- pushed through a high nozzle at high pressure
- a high voltage is applied so that each atom gains a H+ ion
what occurs during electron impact?
an electron gun is shot at the atoms causing an electron to be removed
why is it important during mass spec that the atoms are ionised?
only ions can create a current at the detector
what occurs during acceleration in mass spec?
metal plate has a negative charge which the ions accelerate towards it. all ions gain the same amount of KE
what occurs during ion drift in mass spec?
ion goes down tube with a known length
what occurs at detection in mass spec?
when the ion hits the negative metal plate at the end, 1+ ion picks up an electron creating an electic current. the more ions hit the plate the bigger the current at that moment
why does chromium behave differently in the way its orbitals fill up. write the configuration
3d electrons=5 and 4s=1 , more stable this way
