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Organizing the elements
Objective: How are the elements organized?
Mendeleev developed the first periodic table of the elements.
An element's properties can be predicted from its location in the table.
Link to a Periodic Table.
The modern periodic tableElements are arranged according to atomic number.
Periods (7) = horizontal rows of elements
Group (18 family) = vertical column of elements with similar properties
Zig zag line = separates metals from nonmetals
Br
Ca
Fe
H
C
Cl
Mg
P
Zn
Why the periodic table works?
It works because it's based on the structure of the atoms, especially the valence electrons.
All the elements in a family all have the same number of valence electrons.
http://www.echalk.co.uk/Science/chemistry/periodicTableGame/periodicTable.html
What is a metal?
An element with specific properties: shiny, ductile, malleable, and good conductors of heat and electricity
Usually have 3 or less electrons in outer shell and give up Electrons when forming compounds.
They are found to the left of the zigzag line
Examples: lithium, iron, gold, silver
Review Terms:Review Terms:
Malleable – the ability to be Malleable – the ability to be pounded into thin sheets. pounded into thin sheets.
Ex: aluminumEx: aluminum
Ductile – the ability to be Ductile – the ability to be pulled into a thin wire. Ex: pulled into a thin wire. Ex: coppercopper
AlloysAn alloy is a substance that is a mixture of two or more metals.
Examples: bronze (copper with tin) and brass (copper with zinc)
Metals in the periodic table
Alkali metals (Group 1)
Are the most reactive
Are never found as elements only in compounds
Are very soft and shiny
1 valence electron
Alkaline earth metals (Group 2)
Are not as reactive as Group 1 metals
Are fairly hard, gray-white
Good conductors of electricity
2 valence electrons
Transition metals (Group 3)
Form a bridge between the (left side) very reactive and less reactive (right side)
Are good conductors of electricity
2 valence electrons
Lanthanides and actinides
Rare earth metals (periods 6 and 7).Valence electrons: 2Lanthanides are soft, malleable, shiny metals with high conductivity
• Actinides exist in very small amounts except for thorium and uranium
What are nonmetals?An element with properties opposite of metals: often gases or dull, brittle solids with low melting points
Found to the right of the zigzag line
Forms compounds with metals (e.g., NaCl, CO2)
Combines with other nonmetals to form diatomic molecules (e.g., O2, N2, H2)
ClC
N
OC OO
Properties of Non-Metals Properties of Non-Metals (cont.)(cont.)
Have five or more electrons in Have five or more electrons in their outer shell.their outer shell.
Poor Conductors Poor Conductors
They can share or gain They can share or gain electrons when forming electrons when forming compounds.compounds.
Families of nonmetals
Carbon family: AKA: tetrels – from Latin tetra (four)
4 valence electrons
Families of nonmetals
•Nitrogen family: AKA: pnictide – from Greek pnigein (to choke)
5 valence electrons
Families of nonmetals
Oxygen family: AKA: chalcogens – from Greek chalkos (ore)
6 valence electrons
More families of nonmetals
Halogen family: reactive; found in nature as compounds or diatomic molecules
7 valence electrons
More families of nonmetals
Noble gases: odorless, colorless gases that are not reactive
8 valence electrons
More families of nonmetals
Hydrogen: a very reactive nonmetal because it has 1 valence electron.
This is why it is in the column with the alkali metals. However, it is not classified as an alkali metal.
MetalloidsHave characteristics of both metals and nonmetals
Seven elements on the border between metals and nonmetals
Great conductors of electricity
Examples: B, Si, As, Te, At, Ge, Sb