Presentation on theme: "Unit 3 Notes – Chapter 3 Chemistry 2010-2011 Mr. Nelson."— Presentation transcript:
Unit 3 Notes – Chapter 3 Chemistry Mr. Nelson
Mendeleev Dmitri Mendeleev first organized elements according to atomic mass. He noticed similarities in their chemical properties appeared at regular intervals Such a pattern is called periodic Thing to remember: its just a general trend
Mendeleevs first table
Periodic Law Mendeleevs table has gaps! Two questions he posed: 1. Why could most elements be arranged in order of increasing atomic mass, but some couldnt? 2. What is the reason for chemical periodicity?
Periodic Law Moseley, who worked with Rutherford, discovered that atomic number, not atomic mass, is the basis of organization. This led to… Periodic Law: The physical and chemical properties of the elements are periodic functions of their atomic numbers.
Periodic Table Organization Vertical columns in the periodic table are known as groups or families
Periodic Table Organization Horizontal Rows in the periodic table are known as Periods
Valence Electrons Outer-most electrons
Periodic Table Metals are on the left side of the chart.
Metals Are usually: Lustrous Malleable Ductile good conductors of heat and electricity Tend to lose electrons in chem rxns
Periodic Table Nonmetals are on the right side of the periodic table (with the exception of H).
Nonmetals Are usually Dull brittle poor conductors of heat and electricity. Tend to gain electrons in chem rxns.
Periodic Table Metalloids border the stair-step line (with the exception of Al, Po, and At).
Metalloids Have some characteristics of metals and nonmetals. For Example: Silicon looks shiny, but is brittle and fairly poor conductor.
Alkali Metals: Group 1 Soft! Can be cut like butter with a knife React with O 2 in air Reacts VIGOROUSLY with water
Alkaline-earth Metals Group 2 Harder, denser, higher melting points than group 1. Reactive, but not like group 1. Reacts with oxygen in air, like group 1.
Transition elements Groups 3-12 They are all metals Harder, denser, with higher melting points (except for mercury)
Lanthanides: elements Shiny, reactive metals Actinides: elements All have radioactive forms
Main block elements: groups Named by the uppermost element Halogens: Group 17 Reactive, all are nonmetals.
Noble Gases Group 18 Escaped detection for some time due to their nonreactivity
Hydrogen Group all on its own.
Electron dot diagram Represent valence electrons 1 dot = 1 electron Example: Rubidium
Diatomic Molecules These seven elements occur naturally as molecules containing two atoms.