unit 2 chem atomic structure

mass number

# of protons + # of neutrons

atomic number

ONLY protons

#of protons (in neutral form)

# of electrons

Top number of isotope

mass number (p + n )

bottom of isotope

atomic number (p)

who was the first to propose the concept that all matter is composed of atoms?

greek philosopher democritus but wasn’t accepted until modern times

democritus 

existence of atoms (evidence = logic)

dalton

existence of atoms; combinations of atoms of different elements create compounds (evidence  = whole # ratios of element mass in different compounds)

thompson/rutherford/chadwick

existence of subatomic particles (evidence = observation of charged/neutral particles in matter)

thompson/mosley

atomic mass, atomic number and isotopes (evidence = mass spectrometry and x-ray spectra)

isotope 

same element with different mass numbers

the existence of isotopes violates which of dalton’s original ideas?

the idea that atoms of the same element have the same properties (specifically the same MASS)