chapter 4 the periodic table the chemists most valuable tool
TRANSCRIPT
Chapter 4The Periodic Table
The
Chemists
Most Valuable Tool
Wanted Poster Project
• Due 11/7/14
• Poster Example
Some Review Terms Element Protons Neutrons Electrons Electron
Configuration
Any substance that cannot be separated by ordinary chemical means
Atomic Number When added to
proton the atomic mass
Neg Charged particle equal to protons in a electro neutral atom
Configuration of electrons in an atomFilled sequentially
What is A Periodic Table? An accepted method of organizing
elements by both repetitive chemical and physical properties
How are elements organized?
Key terms
Periodic Law Valence Electrons
Group Period
History: John Newlands While arranging elements in rows
noticed repeating properties Properties seemed to repeat every eight
elements Law of Octaves
Newlands’ Table
Dmitri Mendeleev Orders all 63 known elements Writes symbols and mass number Orders according to similar properties Able to predict missing elements
properties Luther Myer publishes same periodic
table in the following months
1871 Periodic Table
Why Mendeleev’s Able to predict
properties Predicts properties
to yet undiscovered elements
When elements are discovered Mendeleev’s predictions are correct Gallium,scandium & germanium
Henry Moseley Studies x-ray emissions of protons Notices a correlation Recognizes significance of proton as
atomic number Discovery corrects faults with
Mendeleev’s periodic table
Moseley’s Periodic Table
Latest Change Made by Gene Seaborg While working on the Manhatten Project
identifies a new block of elements Moves the Transuranium elements
(atomic number 58-71 and 90-103) Called the Lanthanide and actinide
Series
Henry Moseley Moseley working
with Rutherford using x-rays discovers a pattern
Discovers Atomic Number
Corrects Mendeleev’s Periodic Table
Modern Periodic Law
Is the principle that certain properties of elements occur periodically when arranged by atomic number.
Why? Valence electrons
Number of electrons in the outer most energy level
Is there More? You BET!!!! Energy levels are the horizontal rows
called a Period. So Germanium (Ar) 3d10 4s2 4p2 Highest energy level is a 4p and a
valence number is 4
Tour the Periodic Table Elements are place in groups (columns) and
periods (rows) Main Group Elements
s-block (1 & 2) and p-block orbitals (13-18) Transition elements
Groups 3-12 d-block Transuranium
f -block
4 Main Blocks
Most elements are metals
Nonmetals
Gases and Liquids
A group of its own Can have both a 1+ and a 1- oxidation
state Either be placed into group 1 or 17
Gas Highly reactive Main component of organic molecules
Group 1Alkali Metals Highly reactive Metals Soft, shiny, Single valence electron Dull quickly when exposed to oxygen Reacts with G-17 to form salts React with water to form alkaline
Introducing Alkaline Earth Metals
Group 2 Alkaline earth metals
& Not as reactive as G-1
G1 vs. G2
Group 17Halogen : means generates salts Valence number of 7 Gain 1 electron to make a complete
outer orbital Form acids in water Astatine one of the rarest natural
occurring element
Introducing The Noble Gas Family
Noble gasesGroup 18 Nearly nonreactive
Formally called inert gases 1962 chemists were able to form
compounds with Xe All elements have a full outer orbital
Metalloids Elements located on the zigzag line Properties of
both metals
and nonmetals
Lanthanide and Actinide f-block elements Lanthanide are shiny metals most similar in
reactivity to alkaline earth metals Actinides are unique in that their nuclei break
apart making them highly radioactive Most of the Elements > 93 are man-made
Other Properties of Metals Wide range of melting & boiling points Metals can be mixed with other metals or
elements to make alloys The mixtures have different properties than
the pure substance Brass Cu & Zn
Harder than Cu and non-corrosive Steel Fe & C small amts of Mn or Ni or Cr
Harder, more flexible, less brittle, lighter, less corrosive Sterling Silver Ag & Cu
Atomic Mass Atomic mass of an element is based on
its relative size compare to Carbon-12 1 atomic mass unit (amu) =
1/12 mass of C-12
Symbols
Atomic NumberName
SymbolAverageAtomicMass
6 Carbon
C 12.01
Crystals and Conduction Bands Crystal- a substance in which atoms or
molecules are arranged in an orderly fashion Electrons in the atoms form bonds that bind
the atoms together Electrons are able to move freely through
conduction unoccupied orbitals forming conduction bands
Crystal Lattice Structure
Polar bondsMolecules or elements
Elements packIn tightest configuration
Exploded View
How do metals conduct electricity? Metals overlap Conduction Bands
Band within which electrons must move to allow electrical conduction
Forbidden Zone Lacking in most metals
Conduction bandOverlapping orbital bands
When bands overlap electrons are able to move freely
Partially filled band
Empty orbital
Semiconductors
Small forbidden zone
Filled band
Empty Conduction band
The forbidden zone (energy gap) is smaller so few electrons are able to enter the conduction band
Nonmetals cannot occupy energy levels in the Forbidden zone (large energy gap).
Filled Band
Empty Conduction Band
Large Forbidden Zone (Energy Gap)
This gap prevents all electrons from reaching the conduction band in an insulator
Thermal conductivity High Electrical conductivity in metals =
high thermal conductivity Due to free movement of electrons and
their very low mass Thermal conductivity is also due to the
ability of a crystal to conduct vibrationsDiamonds are poor electrical conductors but very good conductors of heat due to this