Title: ATOMIC AND ELECTRONIC STRUCTURE
1ATOMIC AND ELECTRONIC STRUCTURE
- ? fundamentals of the particles ? quantum theory
and electronic configuration ? the modern
periodic table ?
2Historical Background
- 5 BC - Democritus
- matter consists of very small,indivisible
particles Atomos (uncuttable, indivisible) - 1799 Joseph Louis Proust
- law of definite proportion and multiple
proportions - 1808 John Dalton
- modern atomic theory
3Historical Background
4Daltons Atomic Theory
5Daltons Atomic Theory
6Discovery of the Atomic Structure
- The Electron
- the Cathode Ray Tube
7Discovery of the Atomic Structure
- The Electron
- Joseph John Thomson
- Electron Mass Charge Ratio 1.76 x 108 C/g
8Discovery of the Atomic Structure
- The Electron
- Robert Millikan
- Electron Mass 9.10939 x 10-28 g
9Discovery of the Atomic Structure
10Discovery of the Atomic Structure
- The Proton
- Ernest Rutherford Alpha-Scattering Experiment
11Discovery of the Atomic Structure
- most of the mass of the atom an all of its
positive charge reside in a very small, extremely
dense region nucleus - most of the total volume of the atom is empty
space in which electrons move around the nucleus
12Discovery of the Atomic Structure
- The Neutron
- James Chadwick
- bombarded a thin sheet of beryllium with ?
particles - a very high-energy radiation, similar to ? rays,
was emitted
13Discovery of the Atomic Structure
14Discovery of the Atomic Structure
15Mass Properties of Atoms
- Atomic Number, Z
- gives the charge of the atom
- Mass Number, A
- gives the relative mass of the atom
- Z atomic number
- p number of protons
- e number of electrons
Z p e-
- A mass number
- p number of protons
- n number of neutrons
A p n
16Mass Properties of Atoms
- Isotopes
- atoms of a given element that differ in the
number of neutrons, and consequently, in mass - Nuclide
- an atom of a specific isotope
- way of denoting an element
ZXA
17Mass Properties of Atoms
1H1
1H2
1H3
18Mass Properties of Atoms
- Atomic Mass Unit, amu
- exactly equal to one-twelfth the mass of one
carbon-12 atom - Average Atomic Mass / Atomic Weight
mass of one carbon-12 atom
1 amu
AW ?fractional abundance x isotopic weight
19Properties of Waves
- Wavelength, ?
- distance between successive peaks or troughs
- Cycle
- complete wavelengths
- Frequency, ?
- number of cycles that pass a given point each
second - Amplitude
- maximum oscillation of a wave
c ? ?
20Properties of Waves
- Electromagnetic Radiation
21Quantized Energy and Photons
- Christian Huygens
- light, like sound, is a wave motion
- Isaac Newton
- light is made up of very fast and very small
particles which travel in straight lines - sunlight is composed of various color components
that can be recombined to produce white light - Max Planck
- atoms and molecules could emit (or absorb)
energy only in discrete quantities
22Quantized Energy and Photons
- Quantum
- fixed amount
- smallest quantity of energy that can be emitted
or absorbed as electromagnetic radiation
E h?
- E energy emitted or absorbed
- h Plancks constant
- ? frequency
23Quantized Energy and Photons
- Albert Einstein
- light travel in packets called Photons
-
Energy of a photon E h?
24Bohrs Model of the Hydrogen Atom
- Spectrum
- produced when radiation containing many different
wavelength components is separated - Continuous Spectrum
- spectrum consisting of a continuous range of
colors (i.e., rainbow)
25Bohrs Model of the Hydrogen Atom
- Line Spectrum
- spectrum containing radiation of only specific
wavelengths
26Bohrs Model of the Hydrogen Atom
27Bohrs Model of the Hydrogen Atom
- Johann Balmer
- fitted the wavelengths of the four lines of
hydrogen into a simple formula - Rydberg Equation
- ? wavelength of the spectral line
- RH Rydberg constant
- n positive integers
28Bohrs Model of the Hydrogen Atom
- Neils Bohr
- Only orbits of certain radii, corresponding to
certain definite energies, are permitted for
electrons in an atom. - An electron in a permitted orbit has a specific
energy and is in an allowed energy state. An
electron in an allowed energy state will not
radiate energy and therefore will not spiral into
the nucleus. - Energy is only emitted or absorbed by an electron
as it changes from one allowed energy state to
another. This energy is emitted or absorbed as a
photon, E m?.
n 3
29Bohrs Model of the Hydrogen Atom
- E energy
- RH Rydberg constant
- n quantum number
30Wave Behavior of Matter
- ? wavelength
- h Plancks constant
- m? momentum
- mass x velocity
31Wave Behavior of Matter
32Quantum Mechanics
- Schrodinger Equation
- incorporates both the wavelike and particle-like
behavior of the electron. - Orbital
- describes a specific distribution of electron
density in space
33Quantum Mechanics
- Quantum Numbers
- describe the distribution of electrons in atoms
- derived from the mathematical solution of the
Schrodinger equation for the hydrogen atom - describe the atomic orbitals and label the
electrons that reside in them
34Quantum Mechanics
- Principal Quantum Number, n
- relates to the average distance of the electron
from the nucleus in a particular orbit - determines the energy of the orbital
- referred to as the shell
- values 1, 2, 3
- Angular Quantum Number, l
- describes the way the electron moves around the
nucleus - shape of the probability distribution
- referred to as the subshell
- values 0 to (n 1)
35Quantum Mechanics
36Quantum Mechanics
37Quantum Mechanics
38Quantum Mechanics
- Magnetic Quantum Number, ml
- describes the orientation of the orbital in space
- values -l to l
- Electron Spin Quantum Number, ms
- describes the spin of the electron
- values ½ , -½
39Quantum Mechanics
- Summary
- n shell number of subshells n
- l subshell number of orbitals 2l 1
- n shell number of orbitals n2
40Electronic Configuration
- arrangement of electrons in an atom
- ex Ca 20 electrons
- Orbital Method
- 1s2 2s2 2p6 3s2 3p6 4s2
- Shell Method
-
41Electronic Configuration
- Arrow Method
-
- Core Method
- Ar 4s2
42Electronic Configuration
43Electronic Configuration
- Paramagnetic Substance
- slightly attracted by a magnet
- Diamagnetic Substance
- slightly repelled by a magnet
44Electronic Configuration
45Electronic Configuration
- Valence Electrons
- electrons in the outermost shell
- Lewis Dot Notation
- consists of the symbol of the element and one dot
for each valence electron in an atom of the
element