Atomic Structure Flashcards
Define the atomic no.
No. of protons in the nucleus
Define the mass no.
Total no. of protons + neutrons in the nucleus
Define isotopes
Atoms w/ same no. protons but diff no. of neutrons
What decides the physical properties of an element?
Mass of an atom
What decides the chemical properties of an element?
No. + arrangement of e-
Isotopes of an element have ____ physical properties
Diff
Why do isotopes have the same chemical properties?
Same e- configuration
Who discovered the 1st model of the atom + what was it?
- John Dalton
- Described atoms as solid spheres
- Diff. spheres made up diff. elements
Who discovered the 2nd model of the atom + what was it?
- JJ Thomson
- Plum pudding model
- Discovered e-
- Showed atoms weren’t solid + indivisible
Who discovered the 3rd model of the atom + what was it?
- Rutherford
- Nuclear model - tiny +ve charged nucleus surrounded by cloud of -ve e- - most empty
- Fired +ve charged a-particles at sheet of gold instead of being deflected, most passed straight through
Who discovered the 4th model of the atom + what was it?
- Bohr proposed e- exist in shells of fixed energy
- When e- move btw shells, electromagnetic radiation is emitted
Define the relative atomic mass (Ar)
Average mass of an atom of an element on a scale where an atom of carbon-12 is 12
Define the relative isotopic mass
Mass of an atom of an isotope of an element on scale where an atom of carbon-12 is 12
Define the relative molecular mass (Mr)
Average mass of a molecule on a scale where an atom of carbon-12 is 12
Describe how an ion is formed in a TOF mass spectrometer
- Electronspray ionisation - high v applied in polar solvent, gains H+ ion
- Electron impact ionisation - fire high energy e- at sample, knocks e- off, forming +1 ion
What happens in the 2nd stage of mass spectrometery?
- Acceleration
- +ve charged ions accelerated by electric field
- Same kinetic energy
- Lighter ions move faster
What happens in the 3rd stage of mass spectrometery?
- Ion drift
- Ions enter region w/ no electric field, just drifts
- Lighter ions drift faster
Explain how ions are accelerated, detected + have their abundance determined in a TOF mass spectrometer
- Accelerated by attraction to +ve charged plate
- Detected by gaining e-
- Abundance determinded by size of current flowing in detector
Explain how a current is formed (3)
- +ve ions hit +ve metal plate
- E- flow to +ve ion
- Current produced
- Current proportional to abundance
Suggest what might cause the relative atomic of a sample to be diff from the relative atomic mass given in the periodic table (1)
Some isotopes absent/takes into account other isotopes
Why is it necessary to ionise molecules when measuring their mass in TOF mass spectrometer? (2)
- Only ions will interact w/ + be accelerated by electric field
- Only ions create current when hitting detector
Explain how TOF mass spectrometery distinguishes btw ions w/ diff masses (3)
- +ve ions accelerated by electric field
- To constant kinetic energy
- Lighter ions move faster
- Faster ions arrive first at detector
Outline how to work out relative atomic mass from a mass spectrum
- Multiply abundance + x axis
- Add up total
- Divide by total abundance
Give the full electronic configuration of chromium
[Ar] 4s13d5
