Please enable JavaScript.
Coggle requires JavaScript to display documents.
atomic structure and relative mass - Coggle Diagram
atomic structure and relative mass
history of atomic structure
JJ Thompson-1897
discovered:
-tiny negatively charged particles (electrons).
-sub-atomic particle
plum pudding model
Ernest Rutherford- 1909
scattering of alpha particles using gold foil
1 in 8000 alpha particles ‘reflected’
what Rutherford discovered:
-Alpha particles scatter from the nucleus due to electrostatic repulsion
-All the positive charge and most of the mass concentrated in the nucleus
-Electrons surround the nucleus at relatively large distances
-Atoms are largely empty space
James Chadwick- discovered neutrons
modern view of atom
number of protons = to number of electrons
Overall charge is zero
identification of an element:
by the number of protons
(atomic number)
isotopes
Isotopes:
-atoms of the same element
-different numbers of neutrons
-different masses
-react in the same way
A: Mass number
protons + neutrons
z: atomic number
number of protons
definitions:
Positive ion/cations: fewer electrons than protons (+ve charge)
Negative ions/anions: more electrons than protons (–ve charge)
Transition metals: form several ions with different charges
relative atomic mass
relative atomic mass:
(Ar) is the weighted mean mass
of an element
relative to 1/12th of the mass of an atom of carbon-12
Percentage abundances of isotopes in a sample of an element found experimentally using a mass spectrometer
how mass spectrometers detect Ar?
Ions are accelerated (and deflected)
-heavier ions move more slowly (and are more difficult to deflect than lighter ones).
-Allows separation of each isotope
Ions are detected on mass spectrum as a mass-to-charge ratio, m/z
equation:
relative mass of ion/relative charge of ion
equation of Ar:
Ar = Σ(isotopic mass x % abundance)/100
Ar = Σ(isotopic mass x relative abundance)/total relative abundance
