2.1 Flashcards
Relative atomic mass
The weighted average mass of an atom of an element compared to 1/12 the mass of carbon 12
Ar=
((Isotope mass)x(percentage))+(isotope mass x%)/100
Number of particles is
Moles x avogadros constant
the Greek atom
Democritus said that the division of matter must have a lower limit eventually you would end up with an indivisible particle an atom
Dalton’s atomic theory
atoms are particles that make up elements, atoms cant be divided, all atoms of an element are the same, atoms of one element are different to atoms of another element
jj Thompson and electrons
discovered that cathode rays were a stream of particles(electrons) that were: negatively charged, can be deflected by magnets and electric fields, very small mass
plum pudding model
electrons float in a sea of positive charge - proposed by jj Thompson
Ernest Rutherford’s gold leaf experiment
alpha particles were directed at a gold sheet, most not deflected, some deflected through large angles and few reflected. shows that most of an atom is empty space, positive charge in the middle with most of the mass, overall charges balance
Neil Bohr’s model
altered Rutherfords model so electrons only follow certain paths otherwise they would spiral into the nucleus. explained emission and absorption spectra and the energy of electrons at different distances from the nucleus
what did Rutherford’s discovery of the proton explain
explain the link between atomic number and x-ray frequencies
what are isotopes
when atoms of the same element have a different number of neutrons
why do isotopes of the same element have the same properties
chemical properties are linked to the number of electrons which is linked to the number of protons not neutrons
nitrate ion
NO3 -
carbonate ion
CO3 2-
sulfate ion
SO4 2-
