Atomic Structure Flashcards
What is an isotope?
An atom with the same no. of protons but a different no. of neutrons
Define relative atomic mass
The average mass of an atom of an element relative to 1/12 the mass of a Carbon-12 atom
What is mass spectroscopy used to find?
Abundance and mass of each isotope of an element
What are the 2 types of ionisation for TOF mass spectroscopy?
Electron Impact, Electrospray Ionisation
Explain how electron impact ionisation works
- Sample is vaporised
- Electron gun fires high energy electrons
- One electron from each particle is knocked off, forming +1 ions
Explain how electrospray ionisation works
- Sample is dissolved in volatile solvent
- Sample is injected through hypodermic needle
- Positive needle tip ionises particles by gaining a proton
Which type of ionisation is better for biological molecules and why?
Electrospray, no fragmentation
Describe how positive ions are accelerated in TOF mass spectroscopy
- Using an electric field until all particles have the same kinetic energy
Explain how the flight tube stage of TOF mass spectroscopy works
- Positive ions travel through hole in negative plate and into tube
- TOF depends on velocity which depends on mass alone
How does the detection phase of TOF mass spectroscopy work?
- Positive ions hit negative plate
- Positive ions are discharged by gaining electrons
- Current is generated
How does the detection phase of TOF mass spectroscopy work?
- Positive ions hit negative plate
- Positive ions are discharged by gaining electrons
- Current is generated
What are energy levels divided into?
Sub shells
How many electrons can a sub-shell hold?
2 electrons
How many d-orbitals are there per energy level?
5
What is the 1st ionisation energy?
The energy required to remove 1e- from an atom of 1mol of gaseous atoms of an element
Why should an element be gaseous when measuring ionisation energy?
So energy isn’t used breaking bonds between atoms of that element
Give the 3 factors affecting ionisation energy
Nuclear Charge, Distance from Nucleus, Shielding Effect
Explain how nuclear charge affects ionisation energy
Stronger positive charges attracts electrons more powerfully
How does shielding affects ionisation energy?
Electrons on inner shells reduce the effect of proton charge
Describe how ionisation energy is affected across the periods
- General increase due to increase in nuclear charge
- Shielding and nucleus distance are similar
How is ionisation energy affected down the group?
- General decrease as shielding and nucleus distance increases
- Causes weaker attraction to nucleus so ionisation energy decrease
Describe the solid sphere model
- Small, hard spheres called atoms
- Couldn’t be divided
- Different atoms are different sizes
What discovery did Becquerel make?
Atoms were divisible as particles are emitted from an unstable nucleus
Describe the plum pudding model
A sphere of positive charge with negative electrons embedded in it
