Atomic Structure Flashcards
What is the timeline for the discovery of the atom.
Democritus>John Dalton>J.J Thompson>Rutherford>Niels Bohr>James Chadwick
What did Democritus do?
-He discovered that atoms are in a spherical shape and are indivisible
What did John Dalton do?
He described atoms as solid spheres and said that different spheres made up the different elements
What did JJ Thompson do?
He made the plum pudding model(ball of positive charge with negatively charged electrons) and concluded that an atom must contain even smaller, negatively charged particles.
What did Rutherford do?
He did the alpha scattering experiment.He fired alpha particles at a very thin sheet of gold. From the plum pudding model, he expected most of the alpha particles to be deflected slightly by the positive ‘pudding’ that made up most of the atom.
What were the results of Rutherford’s model?
Most of the alpha particles passed straight through the gold atoms and a very small number were deflected backwards
What did the results of Rutherford’s experiment show him?
There’s a tiny, positively charged nucleus at the centre surrounded by a ‘cloud’ of negative electrons
Most of the atom is empty space
What did Niels Bohr do?
He discovered electron shells
What did James Chadwick do?
Discovered neutrons
What is the relative mass of protons, neutrons and electrons
p:1
n:1
e:1/1840
What is the charge of protons, neutrons and neutrons electrons?
p:+1
n:0
e:-1
What is an isotope?
Atoms of the same size element that contain different numbers of neutrons
What can be said about the reactivity of different isotopes of an element?
The reactivity is identical because they have the same number of electrons
What is the isotope abundance of chlorine-35
75%
What is the isotope abundance of chlorine-37
25%
Define the relative atomic mass
The average mass of its atoms, compared to 1/12th the mass of a carbon-12 atom
What is the percentage abundance of bromine?
50%
How does ionisation work with an electron gun in a ToF
high energy electrons from the gun knock off an electron from each particle in the sample(gas). The particles form a positive charge
What is the ionisation equation for zinc, water and chlorine
Zn(g)->Zn(g)++e-
H20(g)->H20(g)++e-
Cl2(g)->Cl2(g)++e-
How does ionisation work with an electron spray in a ToF
The sample (a solution) is put through a hypodermic needle attached to a positive terminal of high voltage power supply.
The particles gain a proton as they leave the needle spread out in a fine mist because the +ively charged particles are all repelling each other d
Which type of ionisation method is used for large compounds and which are used from small molecules
Electron gun- small molecules
Spray- large compounds
What are the 4 stages in a ToF
1.ionisation
2.acceleration
3.drift region
4.detector
What happens in the acceleration stage?
the positively charge particles are accelerated towards the negatively charged plate
every single particle has the same kinetic energy however lighter particles travel faster as they have a higher velocity
this means that lighter particles get to the detector first
what is the equation for kinetic energy
1/2mv^2