unit one, section one: atomic structure Flashcards
what are protons and neutrons sometimes known as
nucleons as found in the nucleus
what are the relative charges and masses of subatomic particles
neutrons : mass = 1 , charge = 0
protons : mass = 1, charge = +1
electrons : mass = 1/1840 , charge = -1
what force holds protons and neutrons
strong nuclear force , stronger than electrostatic forces , acts over very short distances
what force holds electrons and protons together
electrostatic forces
what is the atomic number (proton number)(bottom num)
number of protons or electrons
what is the mass number (top number)
number of protons and neutrons
define isotope and properties
an atom with same number of proton but different num of neutrons is an isotope
- different isotopes of same element react same as same electron configuration
- mass number may differ due to more neutrons
- physical properties are the same
what is the maximum number of electrons in each sub shell
s = 2 p = 6 d = 10 f = 14
do you fill 3d or 4s first?
4s as technically lower energy level
what do orbital spaces represent
regions of space that electrons are most likely to be in as we can’t know for definite
what is aufbau principle
electrons enter the lowest energy orbital available
what are the rules for allocating electrons to atomic orbitals
1) atomic orbitals of lower energy are filled first
whats Hund’s rule
electrons prefer to occupy orbitals on their own and only pair up when no empty orbitals of the same energy are available (bus)
how does the electron configuration change with ions
electrons in the highest energy levels are lost first HOWEVER lost from 4s before 3d except Cu and Cr
what is the anomaly with Cu and Cr
Using the Aufbau principle, you would write the following electron configurations Cr = [Ar] 4 s 2
3
d
4
Cu = [Ar]
4
s
2
3 d 9 The actual electron configurations are: Cr = [Ar] 4 s 1
3
d
5
Cu = [Ar]
4
s
1
3
d
10
To understand why this occurs, it is important to realize that…
1. Completely filled sublevels are more stable than partially filled sublevels.
2. A sublevel which is exactly half filled is more stable than a partially filled sublevel which is not half full.
3. Electrons are lazy and will do whatever places them in the lowest energy state = which is the most stable state
where do we get evidence for this atomic structure
ionisation energies
what is the definition of 1st ionisation energy
the energy required to remove one electron from each atom in a mole of gaseous atoms producing one mole of 1+ gaseous ions
what is second ionisation energy
energy required to remove the second electron (not both)
describe and explain three factors the ionisation energy
1) distance from the nucleus (atomic radius)
- further away from the nucleus, less attracted to nucleus , easier to remove (less energy req)
2) nuclear charge (draw from protons)
- as go along group higher nuclear charge, protons attract electrons more, smaller radius, harder to remove (more energy req)
3) shielding
- nucleus is shielded by inner electrons , more shells more shielding , weaker attraction between nucleus and outer e’s (less energy req)
what must you specify when talking about attraction
what the attraction is between
why would 3p3 have a stronger ionisation energy than 3p4
in 3p4 there is a pair of electrons , leads for small amount of repulsion as electrons are both neg so easier to remove
why would ionisation energy decrease as another sub shell is added
slight increase in shielding and further away from nucleus so less energy req
what is mass spectroscopy
powerful instrumental technique used to find the relative mass of elements and compounds and identify elements and molecules
name the 4 stages of flight of mass spec
1) ionisation
2) acceleration of ions
3) separation 3of charged ions
4) detection
explain ionisation and the two methods
sample must be ionised to be detected, must be vaporised to ionised
1) electron impact is used for elements and low Mr compounds
- high energy electrons are fired from electron gun to remove a outer electron forming 1+ ion.
- X(g) -> X+(g) + e-
2) electro spray ionisation is used with high Mr compounds
- sampled dissolved in a volatile ( vaporises easily) solvent eg. water and injected through hypodermic needle as fine spray into vacuum (isolate sample)
- needle is positively charged and high voltage at end
- particles gain a proton and become 1+ ions
- X(g) + H+(g) -> XH+ (g)
- solvent evaporates leaving 1+ ions
explain what happens in the acceleration of ions
ions are accelerated using an electric field so that ions have SAME KINETIC ENERGY
- for this to happen the sample MUST be ionised
explain what happens in separation of charged ions
ion drift occurs - ions enter the flight tube , ions with different masses have different time of flight
- lighter ions travel faster and take less time to hit the detector
what happens in detection
the detector is an negatively charged plate to a) attract particles and b) give an electron to pos ions to produce a current
- mass of ion can be calculated by time of flight
- mass spectrum shows abundance of each mass that hit the detector
what do the peaks on a mass spectrum chart show
n of isotopes and abundance
what is the horizontal axis on a mass spectrum chart
mass to charge ratio (m/z)
- in electron impact if 2 electrons are accidentally knocked off this must be accounted for
what is the n+1 peak accounted for
due to existence of carbon 13 and hydrogen 2 - ignore
what is the molecular ion peak
the biggest peak and corresponds to the Mr of the sample
what must you remember with diatomic atoms with mass spec
much more likely to have 2 atoms that form ionic mol
look at chlorine examples
- use probability to work out graph
MUST GO OVER FINDING AR EXAMPLES WITH FOMS
DO IT
suggest what may cause the relative atomic mass of a sample to be different from RAM in periodic table
existence of other isotopes
explain Dalton’s and Thomson’s model
Thomson = plum pudding model in 1897 Dalton = beginning 19th century described atoms as solid spheres
explain Rutherford’s model
1909 fired alpha particles at gold foil. most past straight through but some deflected, positive centre and cloud of electrons
explain Bohr’s model
electrons in fixed orbits and not anything else
each shell has a fixed energy level
when electron moves between shells electromagnetic radiation is admitted or absorbed
radiation fixed frequency
what is the general equation for the nth ionisation
X(n-1)(g) -> Xn + e
mass spec maths
please refer to question book and flash cards
do it!!!!!!!!
explain how ions are detected and relative abundance is measured
- ions hit detector and gain electron
- abundance is proportional to current
