Transcript Arrangement of Electrons In Atoms

Arrangement of Electrons
In Atoms
Objectives
1. Explain relationship between speed, wavelength,
frequency of electromagnetic radiation
2. Discuss the wave-particle duality of light
3. How the photoelectric effect and line-emission spectrum
of hydrogen helped develop the atomic model
4. Describe the Bohr model of the atom
Seeing the Light
c = 3.00 x 10^8 m/s (speed of light)
Consists of particles called photons
Also has wave-like properties
Wavelength (λ) - distance between two
corresponding points on adjacent waves
Frequency (v)- # of waves that pass a point
in any given amount of time
The Visible Spectrum
• Between 380nm – 750nm
• Shorter wavelength is more powerful
(ionizing)
• Blue has shortest wavelength
Energy of a Wave
E = energy (J)
H = Planck’s constant
(6.626 x 10^-34 J*s)
c = 3.00 x 10^8 m/s
λ = wavelength
E
hc

The Eelectromagnetic Spectrum
Bohr Model of the Atom
• Electrons orbit nucleus at
fixed distances
• Electrons can only have
fixed energies at these
distances
• Each orbit called a shell
and is assigned a
quantum number
Shells
• Electrons in shell n =
1 have lowest energy
• Each shell can hold
up to 2n2 electrons
• Innermost shell is
filled first
Quantum Model of the Atom
Objectives
1.
2.
3.
Explain how Heisenberg uncertainty principle and
Shroedinger wave equation led to idea of atomic orbitals
List 4 quantum numbers & their significance
Relate the number of sublevels corresponding to each of
an atom’s main energy levels, the number of orbitals per
energy sublevel, and the number of orbitals per main
energy level
Heisenberg Uncertainty Principle
It is impossible to simultaneously determine
the location and velocity of an electron
Schrödinger Wave Equation
Quantum Theory –
describes mathematically the wave
properties of electrons and other very
small particles
Principle Quantum Numbers
• Symbolized by n
• Value of n are positive integers (1,2,3 etc)
• As n increases, so does its energy and
distance from nucleus
• More than one e- can have the same n
value
• Also called shells or main energy level
• Total number of orbitals in a shell = n2
Angular Momentum Quantum Number
•
•
•
•
•
Symbolized by l
Indicate the shape of the orbital
Also called sublevels
Number of shapes equal to n
Value of l are zero and all positive integers less
than or equal to (n - 1)
Example: n = 2; l = 0 or l = 1
• Each integer is assigned a letter
Example: 0 = s; 1 = p; 2 = d; 3 = f
• n = 2; there are two sublevels s and p
• Each orbital is designated by its principle
quantum number and letter of the sublevel
Example: 1s, 2s or 2p
Magnetic Quantum Number
• Symbolized by m
• Represents orientation of orbital around
the nucleus
• s orbital is spherical; has one orientation
• p orbital is dumbbell shaped; 3
orientations px, py, pz
• m = -1, m = 0, or m = 1
Summary
(n)
(l)
Orbital
Designatio
n
ml
1
0
1s
0
1
2
2
0
1
2s
2p
0
-1,0,1
1
3
2
6
3
0
2
3
3s
3p
3d
0
-1,0,1
-2,-1,0,1,2
1
3
5
2
6
10
0
1
2
3
4s
4p
4d
4f
0
-1,0,1
-2,-1,0,1,2
-3,-2,-1,0,1,2,3
1
3
5
7
2
6
10
14
4
# of
Number of
orbitals electrons
(2n2)
Spin Quantum Number
• Only two possible values
• -1/2 or +1/2
• Any single orbital can hold only two
electrons