CHEM unit 1

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  • Created by: Monica
  • Created on: 22-05-13 19:05



-atomic number - number of protons in the nucleus of an atom

-mass number - number of protons and the neutrons in the nucleus

-isotopes - atoms of the same element with the same number of protons but different number of neutrons

-relative atomic mass (Ar) - the average mass of an element relative to the 12th mass of carbon 12

-relative isotopic mass - the mass on one isotope relative to the 12th mass of carbon 12

-relative molecular mass - the sum of all the relative atomic masses of its consituent atoms

-molar mass - the mass of one mole of substance

-1st ionisation energy - the amount of energy required per mole to REMOVE one electron from each gaseous atom to form a singly positive ion

-1st electron affinity - the energy change per mole for the ADDITION of one electron to a gaseous atom to form a singly negative ion



the sample is turned into gas using an electrical heater


the gas particles are bombarded with high enery electrons to ionise them, electrons are knocked off the particles leaving positive ions, most of the positive ions formed carry a charge of +1 because it is much more difficult to remove further electrons from an already positive ion


the positive ions are accelerated by an electric field


the different ions are deflected by the magnetic field by different amounts


as the magnetic field is slowly increased different ions with a higher mass/charge can reach the detector (stream b) and a mass spectra is produced

the more ions arriving the greater the current


1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 4d10 4f14


-atoms get smaller going across a period LEFT - RIGHT because the nucleur charge increases pulling the electrons in closer though the number of shells is the same

-atoms get bigger going down a group because there are more shells of electrons

-a positive ion is smaller then the neutral atom from which it was made, because the ion has one shell fewer then the atom

-a negative ion is bigger then the neutral ion because the extra repulsion between electrons causes them to spread out


-the general trend is increase going from left to right across a period due to an increased nucleur charge (atomic number) without an increase in the number of inner shielding electrons

-GROUP 3 - it is easier to remove an electron from the higher energy p orbital (decreases ionisation energy)

-GROUP 6 - the repulsion of the two electrons in the p orbital makes it easier to remove one of them



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