chapter 4: atomic structure Flashcards
Who was Democritus?
Among the first to suggest the existence of atoms
What did Democritus believe?
Atoms were indivisible and indestructible
Dalton’s atomic theory
- Discovers an atom using true science
- All elements are composed of tiny indivisible particles called atoms
- Atoms of the same element are identical
- Atoms of different elements combine in simple whole-number ratios to form chemical compounds
- In chemical reactions, atoms are combined, separated, or rearranged – but never changed into atoms of another element.
- Atoms cannot be broken down any further
What are ions?
atoms with more or less electrons than protons
Positive ions
cations
Negative ions
anions
Protons + neutrons =
atomic mass
Number of protons equals…
atomic number
How do we see atoms?
scanning(electron) tunneling microscope
Who discovered the electron?
J.J. Thomson
How did he discover the electron?
cathode ray tube, plum pudding model
Who discovered the mass and charge of a electron?
Robert Millikan
electron’s mass is…
about 2,000 time lighter than a proton or neutron
How did he discover the mass and charge of a electron?
oil drop experiment
Who discovered the proton?
Goldstein
Who discovered the neutron?
Chadwick
Who discovered the nucleus?
Rutherford
How did he discover the nucleus?
gold foil experiment
What did he discover about nucleus?
small, dense, positive
What are atoms composed of?
identical protons, neutrons, & electrons
How are atoms of one element different from another element?
they contain different numbers of PROTONS
Atomic number symbol
Z
Atoms of SAME element can have…
SAME number of protons but DIFFERENT number of neutrons