3.1.1 Atomic Structure Flashcards
3.1.1.1 Fundamental particles 3.1.1.2 Mass number and isotopes 3.1.1.3 Electron configuration
What are the charges of protons?
Positively charged
+1
What are the charges of electrons?
Negatively charged
-1
What are the charges of neutrons?
No charge
0
Why do atoms have no overall charge?
Atoms have an equal number of protons and electrons so have no overall charge
What is the atomic number of an atom?
The number of protons in an atom
What is the atomic mass of an atom?
The number of protons and neutrons
Why is the relative atomic mass sometimes a decimal in the periodic table?
It is the average atomic mass of different isotopes of the same element
What is the formula to work out relative atomic mass?
Relative atomic mass = ((n1mass)+(n2mass)+(n3*mass))/ n1 +n2+n3
What does m/z stand for?
Mass of ion divided by charge number of ion
What is time of flight mass spectrometry?
Mass spectrometry is a very powerful instrumental technique used to accurately find the relative mass of elements and compounds
What is the first stage of time of flight mass spectrometry called?
Ionisation
What is electron impact in stage 1 (Ionisation) of time of flight mass spectrometry used for?
Electron impact is used for elements and low mass compounds (low Mr compounds)
What occurs in electron impact in stage 1 (Ionisation) of time of flight mass spectrometry?
- High energy electrons fired by electron gun at gaseous sample
- Causes atom/molecule to lose an electron
- Atom/molecule forms a positive ion
X(g) - X+(g) + e-
What is electrospray ionisation in stage 1 (Ionisation) of time of flight mass spectrometry used for?
Electrospray ionisation is used for high mass compounds (high Mr compounds) e.g. proteins
What occurs in electrospray ionisation in stage 1 (Ionisation) of time of flight mass spectrometry?
- Sample dissolved in volatile solvent
- Injected from a a fine hypodermic needle as a fine spray into a vacuum in ionisation chamber
- High voltage applied to end of needle so positively charged where spray emerges
- Particles ionised, gaining a proton from the solvent when leaving the needle
- Solvent evaporates leaving positive ions
X(g) + H+ - XH+(g)
What is the purpose of stage 1 (Ionisation) of time of flight mass spectrometry?
- For the sample to become a positively charged ion
- Only ions will be accelerated by electric field
- Only ions create a current
What is the second stage of time of flight mass spectrometry called?
Acceleration of ions
What occurs in stage 2 (Acceleration of ions) of time of flight mass spectrometry?
- Ions are accelerated using an electric field so all ions have the same kinetic energy
KE = 1/2 mvv
Kinetic energy = 1/2* mass of particle * velocity of the particle (squared)
J KG ms-1
What is the third stage of time of flight mass spectrometry called?
Flight tube/Ion drift
What occurs in stage 3 (Ion drift) of time of flight mass spectrometry?
- The ions enter the flight tube with same kinetic energy
- Ions with different masses have a different time of flight
- The lighter ions travel faster and take less time to reach the detector
t=d√m/2KE
time of flight = length of flight tube *(√(mass of particle/2Kinetic Energy))
s m kg J
t=d/v
time of flight = length of the flight tube/ velocty of the particle
s m ms-1
What is the fourth stage of time of flight mass spectrometry called?
Detection
What occurs in stage 4 (Detection) of time of flight mass spectrometry?
- Detector is a negatively charged plate
- Positive ions hit the negative plate producing a current
- The more ions hit the detector, the bigger the current
- The mass of the ions hitting the detector can be calculated from the time of flight
- The mass spectrum shows the number of particles (abundance) of each mass that hit the detector
What is the electronic configuration of Hydrogen? 1 (H)
1s1
What is the electronic configuration of Helium? 2 (He)
1s2
What is the electronic configuration of Lithium? 3 (Li)
1s2 2s1
What is the electronic configuration of Berylium?4 (Be)
1s22s2
What is the electronic configuration of Boron? 5 (B)
1s2 2s2 2p1
What is the electronic configuration of Fluorine? 9 (F)
1s2 2s2 2p5
What is the electronic configuration of Neon? 10 (N)
1s2 2s2 2s6
What is the electronic configuration of Sodium? 11 (Na)
1s2 2s2 2p6 3s1