Atoms Flashcards
When can electrons move up a shell?
When they absorb electromagnetic energy
When can electrons move down a shell?
When they emit electromagnetic energy
How big is the radius of an atom?
1 × 10 to the power of -10 m
How big is the nucleus of an atom?
1/10,000 of the atom size
What is the mass of an electron?
1/2,000
How do you find the average mass of an atom?
abundance x mass number + abundance x mass number
What is an isotope?
An atom with the same number of protons but a different number of neutrons.
What was discovered in 1803?
Atoms are tiny spheres - John Dalton
What was discovered in 1897?
Plum pudding model, atoms are balls of positive charge with negative electrons scattered inside it - JJ Thomson
What was discovered in 1911?
Nuclear model, positive charge concentrated in the nucleus with electrons on the outside - Ernest Rutherford
How was the nuclear model discovered?
Gold foil experiment
What was discovered in 1912?
Electrons are in fixed positions on “energy shells”, they cannot be in between shells. Niels Bohr
What was discovered in 1932?
James Chadwick discovered neutrons.
