Atomic Structure pt1 Flashcards
What does the atomic number represent and what letter is used to represent it
Number of protons in an atom
Z is the letter used to represent the atomic number
What letter represents mass number
A
How is mass number calculated
Number of protons + Number of neutrons= Mass number
Define RAM (Relative Atomic Mass)
Average mass of all isotopes of an element compared to 1/12 of the mass of carbon 12
Define isotope
Atoms with the same number of protons but different number of neutrons.
They have the same chemical properties but different physical properties
How many orbitals and electrons do these letters contain
S,P,D,F
S-1 orbital-2 electrons
P-3 orbitals-6 electrons
D-5 orbitals-10 electrons
F-7 orbitals-14 electrons (this one will rarely be used)
What would be the relationship between 2 electrons in the same orbital in terms of their spin
- Opposite spin
- Repel each other
What are the two elements that do not fit the trend for electronic configuration?
Copper (Ar 4s1 3d10)
Chronium (Ar 4s1 3d5)
They only fill one 4s orbital before filling out the 3d subshell
Why does the mass spectrometer need to be under a vucuum
Because the air particles would ionise and register on the detector
When is electron impact used
For Elements or substances with low formula mass
It can also cause larger organic molecules to fragment
When is electron spray used
For larger organic molecules
True or false:
Fragmentation occurs in electrospray ionisation
False
It does not because the conditions are ‘softer’
What is ionisation
(step 1)
The sample gets ionised( electrospray or electron impact)
How is electron impact done(4)
- A vaporuised sample is injected at low pressure
- An electron gun fires high energy electrons at the sample
- Which knocks out an outer electron
- Forming positive ions with diff charges
How is electro spray ionisation done (4)
- (Sample is) dissolved (in a volatile solvent)
- (Injected through) needle at high voltage/positively
charged - Each particle gains a proton/H+ in the form of a H+ ion X(g)+H^+–>XH+(g)
- The solvent evaporates whilst the ions move to the negative plate
Volatile- Flammable
What is acceleration (step 2 )
When positive ions are accelerated by an electric field to a constant kinetoc energy
Given that all the particles have the same kinetic enegry,Why do some particles go faster than others?
The velocity of the particls depends on its mass
Lighter particles have a faster velocity
Heavier particles have a slower velocity
What is flight tube/ion drift(step 3)
- The positive ions with smaller m/z values will have the same kinetic energy as those with a larger m/z and will move faster
- Heavier ions take longer to move through the drift area
- The ions are distingushed by diff flight times
m/z= mass over charge
Formula for time of flight
t=d/v
T= time of flight (s)
d=length of flight tube (m)
v=Velocity of the partciles (ms^-1)
What is detection(step4)
- Ions hit detector and this causes a current which causes electron flow
- The size of the current is proportional to tge abundance of the isotope
Define Relative molecular mass (Mr)
Average mass of a molecule over 1/12 of the mass of a carbon 12
What is the equation for an electron getting knocked off a sample
x(g)+e^- —> x^+(g) +2e^-
x is just any element
For transition metals, when they are ionised which electron is removed fist in the sub shells? (only applies to d block elements)
the S block is removed first for example Fe is usually [Ar] 4s^2 3d^6
but Fe3+= [Ar] 3d^5
What is the relative mass of an electron
1/1840
