Atoms, Molecules, Atomic Structures

pure substances

elements and compounds

compounds can be broken down to

elements

“atomos”

indivisible, can’t be broken down (atoms)

hypothesis

educated guess

theory

tested

Law

proven over years without exceptions

Dalton’s atomic theory

• matters are made of tiny indivisible particles called atoms

• atoms of same elements are similar

• atoms of different elements are different

  • atoms of different elements combine to form compound atoms (molecules)

Law of Conservation of Mass

every physical/chemical change mass is conserved (mass isn’t created or destroyed)

Law of definite (fixed) proportion

when elements combine to form a compound they do so in fixed proportion by mass

law of multiple proportion

when elements combine to create multiple compounds , masses of one element that combine with the fixed mass of other element, follows whole # ratio

Atoms are made of

subatomic particles or fundamental particles (electron, proton, neutron)

Major atomic structure discoveries were made

1889-1915

Cathode Rays

a stream of negatively charged particles called electrons

Radioactivity

spontaneous emission of energy of particles by a substance

absolute value of charge

1.60 × 10^-19