model of the atom Flashcards
what is an atom
smallest particle of matter and cannot be chemically divided
what have scientists devised in order to represent atoms
various models
what is the dalton billiard ball model
atoms are the smallest, solid units of matter and indivisible
what is j.j thompson model
“plum pudding model”
negative charges distributed in a positive sphere
what did thompson show
the rays could be bent by nearby electric charges
what are negatively charged particles called
electrons
what did thompson add as a part of an atom
negatively charged electrons
what does the cathode ray tube show (observation + conclusion) (3)
- were attracted to the (+) plate = they’re negatively charged
- were easily deflected = they’re light
- made a wheel turn = they had mass (energy)
what did ernest rutherford do
bombarded a thin gold foil with alpha particles
what is the charge of alpha particles
positive
what is the result and conclusion of the first ray
result: went right through
conclusion: atom is mostly empty space
what is the result and conclusion(2) of the second ray
result: 1/1000 was deflected
conclusion: - nucleus was (+), -nucleus was very small
what is the result and conclusion(2) of the third ray
result: 1/100 000 bounced back
conclusion: -nucleus is ~100 000 smaller than than atom, -nucleus is very dense
what is the bohr rutherford atomic model
electrons move in energy levels and that the ones in the outermost orbit determines the chemical properties of that atom
what is a small positive nucleus composed of
protons
what are the protons surrounded by
negatively charged electrons moving in defined orbits
what did james chadwick do
adds the neutrons to the protons in the nucleus
what is a neutron
has no charge, is neutral
what is the simplified atomic model (2)
-protons and neutrons in the nucleus
-surrounded by a number of electrons in each energy shell
what does the number of protons equal
atomic number
what does the number of electrons equal
number of protons
what equal the number of neutrons
atomic mass—atomic number
where is most of the atoms mass
in the nucleus
what is the max # of electrons for the first orbit
2
what is the max # of electrons for the second orbit
8
what is the max # of electrons for the third orbit
8
what is the max # of electrons for the fourth orbit
18
what is the rule for the first 20 elements
2-8-8-2
what is essential before starting another orbit
all orbits before must be filled
