The Electron. 6.0 Chemistry. Development of the Periodic Table. History of the Periodic Table – By the end of the 1700’s, scientists had identified only 30 elements (ex. Cu, Ag, Au, H 2 , N 2 , O 2 , C). By the mid 1800’s, about 60 elements had been identified.
Organized the elements into sets of three with similar properties.
He called these groups triads. The middle element is often the averageof the other two.
Ex) Cl – 35.5
Br – 79.9
I – 126.9
Properties of the elements repeat periodically when the elements are arranged in increasing order by atomic mass
Mendeleev is known as the
Father of Chemistry
#101 honors Mendeleev
died in 1999.
Alkali metals (1) – most reactive metals; reactivity increases down the group
Alkaline earth metals (2)
Boron family (13)
Carbon family (14)
Nitrogen family (15)
Oxygen or Chalcogen family (16)
Noble gases (18) - inert
Transition elements or metals (3-12): d-block
Inner transition elements or metals (f-block)
Lanthanides or lanthanide series
Actinides or actinide series
Transuranium elementsFamily Nameswrite these on your P.T.
- Good conductors of heat & electricity
- High melting points most solids at room temperature
Found on the
LEFT side of
Located on the
RIGHT side of
3. Metalloids - Properties of both metals & nonmetals
- High luster (shiny)
- Ductile (can be drawn into thin wire)
- Malleable (bends without breaking)
- High densities
- Reacts with acids
- Brittle (easy to break)
- No luster (dull)
- Insulators nonconductors
- Neither ductile nor malleable
- Nonreactive with acids
Characteristics of a Wave
ex) Radio FM 93.3 megahertz (MHz) is 93.3 x 106Hz (cycles/sec)
D. Electromagnetic Radiation- a form of energy that exhibits wavelike behavior as it travels through space- all forms of EM radiation move at the speed of light
E. 3.00 x 108 m/s or 186,000 miles/sec.
The relationship between wavelength and
frequency can be shown with the following
This is an indirect relationship.
If λ then ν .
c = λ ν
(Think steps not a ramp)
E = h
Planck’s equation for each quantum
h = Plank’s constant = 6.626 x 10-34 J.s
This is a direct relationship.
As energy increases, frequency increases.
While well-known for the equation E=mc2 , Einstein’s work on the photoelectric effect resulted in being awarded the 1921 Nobel Prize in Physics.
(1879 – 1955)
Refers to the emission of electrons from a metal when light shines on the metal
Definition: a method of studying substances that are exposed to some sort of continuous exciting energy.
A. Emission Line Spectra: contains only certain colors or wavelengths ( ) of light.
1. Every element has its own linespectrum (fingerprint).
Line Spectrum – Excited Elements
A Line Spectra result from excited elements - as electrons of an element gain energy and rise to an excited state they then fall back to their ground state in the same pattern producing the same energy drop each time which we see as individual wavelengths of light.
Neils Bohr - Danish Scientist
Explained the bright-line spectrum of hydrogen
Result: Hydrogen emitted 4 distinct bright lines of color, aka bright line spectrum
Electrons absorb energy to rise to a higher or excited state and emit energy in the form of a photon of light as they fall back to their ground states.
H(g) + energy H+1(g) + 1e-
Calculated ionization E = observed ionization E
= 1312.1 kJ/mol
n=2 n=3 n=4 n=5 n=6 n=7
Electrons are not stable. Radiation (light) is emitted when an electron falls back from a higher level to a lower level.
Although Bohr’s atomic model explained the line spectra of hydrogen, it failed for heavier elements.
**Large objects obey the laws of classical mechanics**
Four quantum numbers in the equation are used to describe an electron’s behavior – location and energy.
Electron is treated as a wave with quantized energy.
Describes the probability of the electrons found in certain locations around the nucleus.D. Erwin Schrödinger Wave Equation (1926)
(1887 – 1961) Austrian Physicist
An orbital is a region in
which an electron with a
particular energy is likely
to be found.
Where the density of an
electron cloud is high there
is a highprobability that is
where the electron is
located. If the electron
density is low then there is
E. Atomic Orbitals - region around the nucleus where an electron with a particular energy is likely to be found (not the same as Bohr’s orbits!)
2. Orbitals do not describe how the electronmoves.
3. The drawing of an orbital represents the 3-dimentionalsurface within which the electron is found 90% of the time.
s – orbital spherical
For a more complete representation and presentation of atomic orbitals go to http://winter.group.shef.ac.uk/orbitron/
zx2-zy2, xyz, 5xz2-3xr2, 5z3-3zr2)
+1/2 or -1/2 or or
1. Each orbital can only hold 2 electrons.
2. The electrons must have opposite spins.
s-sublevel = max 2electrons
p-sublevel = max 6 electrons
d-sublevel = max 10 electrons
f-sublevel = max 14 electrons
incorrect ↑↓↑ __
correct ↑ ↑ ↑
Pauli Exclusion Principle: No more than 2 e- are put in each orbital and they must have opposite spin.
Hund’s Rule: electrons spread out among equal energy orbitals in a sublevel (like charges repel)
Aufbau Principle: Electrons fill lowest energy levels first (n=1)
Ex) electron configuration for Na:
1s2 2s2 2p6 3s1
Ex) orbital filling box diagram for Na:
Write the symbol for the element.
Place dots around the symbol to represent the
valences & p electrons only.
Do NOT include d & f orbitals in diagram.
p orbital electronss orbital electrons
What does the Tellurium electron-dot resemble???
Draw the Dot Diagrams for these elements
Carbon has 4 valence electrons