3.1.1 Atomic structure Flashcards
What is the relative mass and charge of a proton?
mass = 1
charge = +1
What is the relative mass and charge of an electron?
mass = 1/1840
charge = -1
What is the relative mass and charge of a neutron?
mass = 1
charge = 0
What did John Dalton discover?
All matter is made from atoms, atoms can’t be broken into anything smaller
What did Thomson discover?
negatively charged electrons, ‘plum pudding model’.
What did Rutherford discover?
established nucleus was positively charged, electrons are outside nucleus, ‘gold foil experiment’,
What did Bohr discover?
detailed explanation of atomic structure, electrons arranged in shells.
What did Chadwick discover?
neutron
What is mass spectrometry used for ?
find mass and abundance of each isotope in an element.
help identify molecules by determining relative mr.
What happens in electron impact ionisation?
sample is vaporised and high energy electrons from electron gun are fired at it. High energy electrons able to remove outermost electron of a gaseous atom or molecule. causes fragmentation.
Equation for electron impact ionisation?
M(g) - M+(g) + e-
What happens in electrospray ionisation?
sample dissolved in volatile solvent and injected through thin hypodermic needle to give fine mist. needle tip attached to positive terminal so particles ionised by gaining a proton.
equation for electrospray ionisation?
M + H+ - MH+
What happens during acceleration stage in TOF?
positive ions accelerated using electric field so all ions have same kinetic energy and speed depends on their mass.
What happens during detection phase of TOF ?
positive ions strike negatively charged plate, positive ions neutralised by gaining an electron, generates a flow of electrons and a current that is amplified to produce a signal.
Why does atomic radius decrease across a period?
Number of protons increases so nuclear charge increases. Shielding remains the same so attraction increases between nucleus and outermost energy level.
Why does atomic radius increase down a group?
shielding increases, attraction between nucleus and outermost electron decreases due to energy level being further away, nuclear charge increases down the group.
Define first ionisation energy.
the energy required to remove the outermost electron from one mole of gaseous atoms of an element to form one mole of gaseous ions.
enthalpy change when:
M(g) - M(g)+ + e-
why do we see a general increase in ionisation energies across period 3?
nuclear charge increases, shielding remains the same, attraction between outermost electron and nucleus increases, more energy required to remove an e-.
