Transcript Modern Atomic Theory

Modern Atomic Theory
4.3
Bohr’s model
A.
B.
Concentrated on placement of electrons
around the nucleus
Looks like planets revolving around the
sun
C.
D.
E.
Electrons move at constant speed in
fixed orbits around nucleus
Electrons can gain or lose energy by
moving to different energy levels (also
called shells)
When electrons move to a lower energy
level, they emit light or give off heat
Electron Cloud Model
A.
B.
Electrons don’t really move in a
predictable way, like the planets in the
solar system
Electron cloud model shows the most
likely location of electrons
1. Hard to predict exactly where they are
Atomic Orbitals
A.
B.
Orbital – space around the nucleus
where an electron is likely to be found
1. electron cloud represents all the
orbitals in an atom
Each energy level has different number
of orbitals
Energy Level
Number of
Orbitals
Max. # of
Electrons
1 (K)
1
2
2 (L)
4
8
3 (M)
9
18
Electron Configuration
A.
B.
Electron configuration – the arrangement
of electrons in the orbitals of an atom
The most stable electron configuration is
one in which the electrons are in the
lowest possible orbital – this is the
ground state
C.
D.
When electrons move away from the
ground state to a higher orbit, they
become “excited” and the atom is less
stable
When the electrons move back to the
ground state, they give off light
Example: neon, argon, xenon