unit 2 - atom and elements Flashcards
what was john dalton’s theory?
atoms are very small particles, atoms of the same element are identical to each other, atoms of different elements are not
who developed the plum pudding model?
j.j. thomson
what did jj. thomson contribute to chemistry?
-he discovered the electron
- proposed the plum pudding model
- experimented with cathode ray tubes
what did ernest rutherford contribute?
- gold foil experiment
- he proposed the nuclear structure of the atom where the heavy nucleus of positive charge is surrounded by many light electrons
what was the gold foil experiment? what did it prove?
- he shot alpha particles onto a gold foil and discovered that some particles deflected off
- showed that gold foil atoms are mostly empty space with a tiny dense positively charged nucleus
Who proved that neutrons exist?
james chadwick
what did niels bohr work on?
- theorized that electrons moved in orbits around the nucleus
where is atomic number located?
top left corner
where is the atomic mass located?
under element name
how do you find the number of protons in an element?
atomic number
how do you find the number of electrons in an element?
atomic number
how do you find the number of neutrons in an element?
(mass number) - (atomic number)
what’s the difference between atomic mass and atomic number?
The atomic number is the number of protons in the nucleus of an atom. The atomic mass is the mass of one atom of that element.
what are 4 properties that dmitri mendeleev used for organizing the elements?
mass, colour, density, melting point
which elements are gases at room temperature?
chlorine, hydrogen, fluorine, oxygen, nitrogen, all the noble gases
