Chapter 4 The Structure of an Atom

atomic number

number of protons in a particular element

# of protons=

#of electrons if neutral

Dalton's atomic theory

-all matter is composed of particles called electrons - atoms of a specific element are different from other - Cannot be created divided or destroyed

mass of an electron

1/1840 of hydrogen atom

Half Life Formula

A=A0(1/2)^(t/h)

Why was Democritus theory rejected?

Aristotle's major criticism concerned idea that atoms moved through empty space and did not believe that the nothingness of empty space could exist. Also Democritus could not test his ideas

What did many Greek philosophers think that matter was made of?

air, earth, fire, water

Robert Millikan

determined charge of electron

JJ Thomson

determined charge to mass ratio of charged particle with cathrode ray mass of charged atom was less than the hydrogen atom

The Greek Philosopher Democritus

first person to propose the idea that matter was not infinitely invisible. he believed matter was made up of tiny individual particles called atomos. Atoms could not be created, destroyed or further divided

Charge=

protons-electrons

what instrument allows us to see individual atoms

scanning tunneling microscope

John Dalton

schoolteacher in England who found electrons with cathrode ray tube

Atom

smallest particle of an element that retains the properties of that element

Ruthford

used gold foil to discover nucleus and