c1 Atomic Structure Flashcards
neutron
relative mass of 1
no charge
proton
relative mass of 1
1+ charge
elements are determined by number of protons
Isotopes
different form of the same element
different number of neutrons
same atomic number, different mass number
eg carbon-12 6 proton, 6 neutron
carbon-13 6 proton, 7 neutron
formula for relative atomic mass
sum of all (isotope abundance(%) * isotope mass)/abundance of all isotopes
compounds
two or more element in fixed proportions held together by chemical bonds
what is an element
if a substance only contains atoms with the same number fo protons it is an element
how many elements are there
about 100
John Dalton
early 19th century
atoms are different spheres and different spheres makes up elements
JJ thompson
1897
electron - his measurements of charge and mass showed that there are smaller particles
new theory known as the ‘plum pudding model’
plum pudding model
ball of positive charge with negative electron in it
Ernest Rutherford and Ernest Marson
1909
alpha particle scatter experiments
few particles are deflected - tiny positively charged nucleus
cloud of negative electrons surrounds this nucleus - most of the atom is empty space
direct hit with the nucleus the particle were deflected backward, if near then it is deflected
came up with the nuclear model
(however the electrons would collapse if its like cloud. shells? bohr ?)
james chadwick
Bohr’s nuclear model
contain shells
electron orbit the nucleus in fixed shells
this was supported by many experiments and explains lots of observations at the time
James Chadwick
neutrons
updated the model which made it pretty similar to today’s nuclear model
electron shell rules
electron always occupy shells (energy levels)
lowest energy must be filled first
certain amount of electron in each shell:
2,8,8
