Atomic Structure Flashcards
(40 cards)
Who was first in the history of the atom timeline
Democritus
What did Democritus claim/discover?
He that matter are made up of indivisible particles or atoms.
Who was second in the history of the atom timeline?
John dalton
What did John Dalton discover?
He developed understanding of atomic theory and came up with theories about what made up different elements.
Who was third in the history of the atom timeline?
JJ Thomson
What did JJ Thomson discover?
He discovered that atoms are made up of a ball of positive charge with negative electrons dispersed randomly. This is called the plum pudding model.
Who was fourth in the history of the atom timeline?
Rutherford
What did Rutherford discover?
Ernest Rutherford conducted his famous gold foil experiment and fired postitively charged alpha particles at a very thin sheet of gold. From the plum pudding model they were expecting most of the alpha particles to be deflected slightly by the positive ‘pudding’ that made up most of an atom. However they discovered that most of the alpha particles passed straight though the gold atoms and a very small number were deflected backwards which allowed him to come up with the idea that there’s a tiny positively charged nucleus at the centre surrounded by a ‘cloud’ of negative electrons. Most of the atom is empty space
Who was fifth in the history of the atom timeline?
Niels bohr
What did Niels bohr discover?
He proposed a new model of the atom with the four basic principles.(the nuclear model)
-electrons only exist in fixed orbits (shells)and not anywhere in between
-each shell has a fixed energy
-when an electron moved between shells electromagnetic radiation is emitted or absorbed
-Because the energy of shells is fixed, the radiation will have a fixed frequency.
Who was fifth in the history of the atom timeline?
James Chadwick
What did James Chadwick discover?
He discovered neutrons. He was last to discover this as neutrons live in the nucleus which is very small. Neutrons have no charge
what are ‘things’ that live in the nucleus called?
nucleons/subatomic particles
Calculate the PEN number of Cl-
P:17 E:18 N:18
Calculate the PEN number of Cr3+
P:24 E:21 N:28
What is an isotope?
An isotope is an atom of an element that has the same number of protons and electrons but different number of neutrons
What is the relative atomic mass of Cl?
35.5
The isotopes of Cl are 35 and 37, explain why the RAM is 35.5
There is an uneven distribution of the isotopes as there is 75% of Cl35 and only 25% of Cl37
Which isotope of Chlorine 35 or 37 is more reactive and why?
Neither one of the chlorine isotopes are more reactive than the other they both have the same number of electrons so both have the same electron configuration therefore they react the same.
What are the distributions of 35Cl 37Cl and 79Br 81Br
35Cl is 75% 37Cl is 25%
79Br is 50% 81Br is 50%
State the four stages of the time of flight mass spectrometer in order
-ionisation
-acceleration
-drift area
-detector
Describe the stages of the TOF mass spectrometer (electron impact)
1)ionisation
-Gives every single atom a 1+ charge
-sample is super heated so it is vaporised (separates all the individual atoms)
-Gaseous atoms are bombarded with electrons with an electron gun firing high energy electrons at the sample to knock off an electron
-left with an ionised sample that has a positive charge
2)acceleration
-charged plates create an electric field.
-when ions get near the electric field they are all accelerated forwards with the same kinetic energy, but with different velocities due to their differences in mass.
-Lighter ions will travel faster and heavier ions will travel slower.(greater the mass, the lower the velocity)
3)flight tube
-the process of ion drift occurs where the heavier ions travel slower and are at the back whilst the lighter ions travel faster and are at the front, which is what enables the machine to separate out the individual isotopes from each other.
4)detection
-positive ions hit negative metal plate(detector) and gain electrons which creates an electrical current due to flow of flow of electrons as through +ve ions hit the detector. The size of current is proportional to the abundance of each isotope
-The current is monitored and analysed to give a spectra
What does that TOF mass spectrometer do?
It detects the mass and the relative abundance of isotopes
State why there are two electrons given after ionisation has taken place in the TOF mass spectrometer
-one of them is the electron that was fired at the sample
-one of them is the electron that was knocked off the sample
