1.0 Atomic structure Flashcards
Describe the atomic model proposed by JJ Thompson
- Plum pudding model
- Sphere of positive charge with electrons dotted throughout
Describe the experiment of Rutherford where he discovered the nucleus
- Fired alpha particles at gold
- Some deflected and bounced back showing small centres of positive charge
Describe the atomic model proposed by Bohr
Positive nucleus surrounded by electrons in defined shells
What are the relative masses and charges for each subatomic particle?
Mass:
Proton = 1
Neutrons = 1
Electron = 1/1840
Charge:
Proton = +1
Neutron = 0
Electron = -1
What letters are used to represent mass and atomic number?
Mass number = A
Atomic number = Z
How are positive and negative ions formed?
Positive = loss of electrons
Negative = gain of electrons
Define isotope
Atoms of the same element with different numbers of neutrons
Why do isotopes have the same chemical properties?
Same electron configuration
What are the two main uses of mass spectrometry?
- To find the abundance of each isotope in an element to be able to determine the Ar of an element
- To find the relative molecular mass of substances made of molecules
What are the four main stages of mass spectrometry?
- Ionisation
- Acceleration
- Flight tube or drift
- Detection
What are the two methods of ionisation that could be used in a mass spectrometer?
Electron impact
Electrospray
Write a generic equation to show the ionisation of X by electron impact
X (g) → X+ (g) + e-
Describe what happens during electrospray ionisation
Each particle gains a proton
Write a generic equation to show the ionisation of X by electrospray mass spectrometry
X + H+ → XH+
Compare the speed and kinetic energy of a lithium and potassium atom in OF mass spectrometry
- Lithium faster as it is a smaller atom
- Both have the same kinetic energy
What is meant by the molecular ion peak?
The highest m/z value on the spectrum of a molecule, formed when the molecule does not break up
How are ions detected in a TOF mass spectrometer?
Ions hit the detector and gain electrons, which induces a current to flow
How can you determine the number of ions hitting the detector at a m/z value?
The size of the current indicates how many ions are hitting the detector
Define principal energy level
One of the 7 main energy levels in an atom which an electron may reside
Define principle quantum number
The number, n, used to label the principle energy levels
What are the regions where electrons are likely to be found called?
Electron orbitals
How many electrons can each orbital hold?
S = 2
P = 6
D = 10
What is the Pauli exclusion principle?
Each orbital can hold a maximum of 2 electrons
What is the Aufbau principle?
The lowest sub-levels are occupied first
