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