Unit 2 – Electrons and Periodic Behavior : Unit 2 – Electrons and Periodic Behavior Cartoon courtesy of NearingZero.net
The Bohr Model of the Atom : The Bohr Model of the Atom Neils Bohr I pictured electrons orbiting the nucleus much like planets orbiting the sun. But I was wrong! They’re more like bees around a hive. WRONG!!!
Quantum MechanicalModel of the Atom : Quantum MechanicalModel of the Atom Mathematical laws can identify the regions outside of the nucleus where electrons are most likely to be found. These laws are beyond the scope of this class…
Schrodinger Wave Equation : Schrodinger Wave Equation Equation for probability of a single electron being found along a single axis (x-axis) Erwin Schrodinger
Heisenberg Uncertainty Principle : Heisenberg Uncertainty Principle You can find out where the electron is, but not where it is going. OR… You can find out where the electron is going, but not where it is! “One cannot simultaneously determine both the position and momentum of an electron.” Werner
Heisenberg
Electron Energy Level (Shell) : Electron Energy Level (Shell) Generally symbolized by n, it denotes the probable distance of the electron from the nucleus. Number of electrons that can fit in a shell: 2n2
An orbital is a region within an energy level where there is a probability of finding an electron. This is a probability diagram for the s orbital in the first energy level… : Orbital shapes are defined as the surface that
contains 90% of the total electron probability. An orbital is a region within an energy level where there is a probability of finding an electron. This is a probability diagram for the s orbital in the first energy level…
Energy Levels, Sublevels, Electrons : Energy Levels, Sublevels, Electrons
Sizes of s orbitals : Orbitals of the same shape (s, for instance) grow
larger as n increases… Nodes are regions of low probability within an
orbital. Sizes of s orbitals
s orbital shape : The s orbital has a spherical shape centered around
the origin of the three axes in space. s orbital shape
P orbital shape : There are three dumbbell-shaped p orbitals in
each energy level above n = 1, each assigned to
its own axis (x, y and z) in space. P orbital shape
d orbital shapes : Things get a bit more complicated with the five d orbitals that are found in the d sublevels beginning with n = 3. To remember the shapes, think of “double dumbells” …and a “dumbell
with a donut”! d orbital shapes
Shape of f orbitals : Shape of f orbitals
Orbital filling table : Orbital filling table
Pauli Exclusion Principle : Pauli Exclusion Principle Two electrons occupying the same orbital must have opposite spins Wolfgang
Pauli
Electron Spin : Electron Spin Electron spin describes the behavior (direction of spin) of an electron within a magnetic field. Possibilities for electron spin:
Electron configuration of the elements of the first three series : Electron configuration of the elements of the first three series
Slide 18 :
Irregular conformations of Cr and Cu : Irregular conformations of Cr and Cu Chromium steals a 4s electron to half
fill its 3d sublevel Copper steals a 4s electron to FILL
its 3d sublevel
Wave-Particle Duality : Wave-Particle Duality JJ Thomson won the Nobel prize for describing the electron as a particle. His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron. The electron is a particle! The electron is an energy wave!
The Wave-like Electron : The Wave-like Electron Louis deBroglie The electron propagates through space as an energy wave. To understand the atom, one must understand the behavior of electromagnetic waves.
Electromagnetic radiation propagates through space as a wave moving at the speed of light. : c = C = speed of light, a constant (3.00 x 108 m/s) = frequency, in units of hertz (hz, sec-1) = wavelength, in meters Electromagnetic radiation propagates through space as a wave moving at the speed of light.
Types of electromagnetic radiation: : Types of electromagnetic radiation:
The energy (E ) of electromagnetic radiation is directly proportional to the frequency () of the radiation. : E = h E = Energy, in units of Joules (kg·m2/s2) h = Planck’s constant (6.626 x 10-34 J·s) = frequency, in units of hertz (hz, sec-1) The energy (E ) of electromagnetic radiation is directly proportional to the frequency () of the radiation.
Wavelength Table : Long
Wavelength
=
Low Frequency
=
Low ENERGY Short
Wavelength
=
High Frequency
=
High ENERGY Wavelength Table
Spectroscopic analysis of the visible spectrum… : …produces all of the colors in a continuous spectrum Spectroscopic analysis of the visible spectrum…
Spectroscopic analysis of the hydrogen spectrum… : …produces a “bright line” spectrum Spectroscopic analysis of the hydrogen spectrum…
Electron transitionsinvolve jumps of definite amounts ofenergy. : This produces bands
of light with definite
wavelengths. Electron transitionsinvolve jumps of definite amounts ofenergy.
Mendeleev’s Periodic Table : Mendeleev’s Periodic Table Dmitri Mendeleev
Modern Russian Table : Modern Russian Table
Stowe Periodic Table : Stowe Periodic Table
A Spiral Periodic Table : A Spiral Periodic Table
“Mayan” Periodic Table : “Mayan” Periodic Table
The Periodic Table : The Periodic Table Period Group or family Period Group or Family
The Properties of a Group: the Alkali Metals : Easily lose valence electron
(Reducing agents)
React violently with water
Large hydration energy
React with halogens to form
salts The Properties of a Group: the Alkali Metals
Properties of Metals : Properties of Metals Metals are good conductors of heat and electricity
Metals are malleable
Metals are ductile
Metals have high tensile strength
Metals have luster
Examples of Metals : Examples of Metals Potassium, K reacts with water and must be stored in kerosene Zinc, Zn, is more stable than potassium Copper, Cu, is a relatively soft metal, and a very good electrical conductor. Mercury, Hg, is the only metal that exists as a liquid at room temperature
Properties of Nonmetals : Properties of Nonmetals Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element. Nonmetals are poor conductors of heat and
electricity
Nonmetals tend to be brittle
Many nonmetals are gases at room temperature
Examples of Nonmetals : Examples of Nonmetals Sulfur, S, was once known as “brimstone” Microspheres of phosphorus, P, a reactive nonmetal Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure
Properties of Metalloids : Properties of Metalloids Metalloids straddle the border between metals and nonmetals on the periodic table. They have properties of both metals and nonmetals.
Metalloids are more brittle than metals, less brittle than most nonmetallic solids
Metalloids are semiconductors of electricity
Some metalloids possess metallic luster
Silicon, Si – A Metalloid : Silicon, Si – A Metalloid Silicon has metallic luster
Silicon is brittle like a nonmetal
Silicon is a semiconductor of electricity Other metalloids include: Boron, B
Germanium, Ge
Arsenic, As
Antimony, Sb
Tellurium, Te
Determination of Atomic Radius: : Half of the distance between nucli in
covalently bonded diatomic molecule "covalent atomic radii" Periodic Trends in Atomic Radius Radius decreases across a period Increased effective nuclear charge due
to decreased shielding Radius increases down a group Addition of principal quantum levels Determination of Atomic Radius:
Table of Atomic Radii : Table of Atomic Radii
Ionization Energy - the energy required to remove an electron from an atom : Increases for successive electrons taken from
the same atom Tends to increase across a period Electrons in the same quantum level do
not shield as effectively as electrons in
inner levels Irregularities at half filled and filled
sublevels due to extra repulsion of
electrons paired in orbitals, making them
easier to remove Tends to decrease down a group Outer electrons are farther from the
nucleus Ionization Energy - the energy required to remove an electron from an atom
Table of 1st Ionization Energies : Table of 1st Ionization Energies
Ionization of Magnesium : Ionization of Magnesium Mg + 738 kJ Mg+ + e- Mg+ + 1451 kJ Mg2+ + e- Mg2+ + 7733 kJ Mg3+ + e-
Electronegativity : Electronegativity A measure of the ability of an atom in a chemical
compound to attract electrons Electronegativities tend to increase across
a period Electronegativities tend to decrease down a
group or remain the same
Periodic Table of Electronegativities : Periodic Table of Electronegativities
Summation of Periodic Trends : Summation of Periodic Trends
Ionic Radii : Ionic Radii Cations Positively charged ions formed when
an atom of a metal loses one or
more electrons Smaller than the corresponding
atom Anions Negatively charged ions formed
when nonmetallic atoms gain one
or more electrons Larger than the corresponding
atom
Table of Ion Sizes : Table of Ion Sizes