Download Intro to Chapter 5 Development of the Periodic Table

Chapter 5: Periodicity and Atomic Structure
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
5.13
5.14
5.15
Development of the Periodic Table
Light and Electromagnetic Spectrum
Electromagnetic Radiation and Atomic Spectra
Particlelike Properties of Electromagnetic Radiation: The Planck Equation
Wavelike Properties of Matter: The de Broglie Equation
Quantum Mechanics and the Heisenberg Uncertainty Principle
Wave Functions and Quantum Numbers
The Shapes of Orbitals
Quantum Mechanics and the Atomic Spectra
Electron Spin and Pauli Exclusion Principle
Orbital Energy Levels in Multielectron Atoms
Electron Configurations of Multielectron Atoms
Electron Configurations and the Periodic Table
Some Anomalous Electron Configurations
Electron Configurations and Periodic Properties: Atomic Radii
Intro to Chapter 5
The periodic table is the most important organized principle in
chemistry.
If you know the properties of any one element in a group, or column,
you can make a good guess at the properties of every other other element
in the same group. In this chapter we will discover why the elements
follow specific periodic trends by examining the intriguing atomic
structures of the elements.
Development of the Periodic Table
A. Creation of the Periodic Table by Mendeleev in 1869 is an ideal
example of how scientific theory comes into being. Through random
observations followed by organization of data into trends resulted in a
consistent hypothesis which could explain known facts and makes
correct predictions of the elements.
B. Mendeleev s organized chemical information by:
1) listing elements by atomic weight
2) grouping them together according to chemical reactivity
1
Light and the Electromagnetic Spectrum
What properties of atoms is responsible for the periodic variations?
To understand how, it s necessary to look first at the nature of visible
line and other forms of radiant energy. Historically, studies of the
interaction of radiant energy with matter provided immense insight
into the atomic structures. Visible light, infrared, microwaves, X-rays
etc are all different kinds of electromagnetic radiation . Collectively
they make up the Electromagnetic spectrum.
A. Radiant Energy- has wavelike properties.
Three components: 1) frequency ( ) - the number of peaks that pass by a fixed
point per unit of time [ s-1 or Hz]
2) Wavelength ( ) - the length from one wave maximum to
the next
3) Amplitude- the height measured from the middle to the
maximum the intensity of energy is proportional to its
amplitude
2
B. Speed of light ( c ) - rate of travel of all electromagnetic radiation in a
vacuum.
1. c = 3.00 x 108 m/s
2. Wavelength x frequency = speed of light
(m) x (s-1) = c (m/s)
Frequency and wavelength are inversely
related
= c
long ; low
short ; high
EXAMPLE: Calculate the wavelength , in meters and nanometers, of radiation
with a frequency of 1.18 x 1014 s-1
What region of the electromagnetic spectrum is it?
ANSWER: Using
= c
= 3.00 x 108 m/s
= 2.54 x 10-6 m
1.18 x 1014 s-1
= 2.54 x 10-6 m x 109 nm = 2,540 nm
1m
This wavelength found in infrared region (see Figure 5.3).
Electromagnetic Radiation and Atomic Spectra
A.
Individual atoms give off radiation when heated or otherwise
excited energetically.
1. Provides important clues to the atomic makeup
2. Electromagnetic radiation from excited atom consists of
only a few .
3. The resulting Line Spectrum- series of discrete lines (or
wavelengths) separated by blank areas (no radiation).
4. Each element has its own unique line spectrum
B. Balmer and Rydberg- discovered a pattern in atomic line spectra
for the hydrogen which fits the generalized equation:
1=R( 1 - 1)
m2 n2
This equation will be discussed again, in detail. when we deal the
concept of Quantized energy
3
Line spectra for (a) sodium and (b) hydrogen
4
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