periodic table

Periodic table

Elements arranged by atomic number

Groups

Vertical columns with similar properties

Periods

Horizontal rows in the periodic table

Group properties

Elements in the same group have the same outer electrons

Atomic number

Number of protons in an atom

Reactivity and electrons

Reactivity depends on outer shell electrons

Early periodic tables

Elements arranged by atomic weight

Problems with early tables

Some elements were in wrong groups

Mendeleev

Left gaps and changed order for undiscovered elements

Mendeleev predictions

New elements discovered filled the gaps

Isotopes

Explained why atomic weight order was not always correct

Metals

Elements that form positive ions

Non-metals

Elements that do not form positive ions

Metal location

left side

Non-metal location

right side

Metal properties

Good conductors, shiny, malleable

Non-metal properties

Poor conductors, dull

Group 0

Noble gases with full outer shells

Noble gases

Very unreactive elements

Helium

Has only 2 outer electrons

Group 0 boiling points

Increase down the group

Group 0 trend

Atoms get larger down the group

Group 1

Alkali metals with 1 outer electron

Group 1 with water

Produces hydrogen and alkaline solution

Group 1 with oxygen

Forms metal oxides

Group 1 with chlorine

Forms white metal chlorides

Group 1 reactivity

Increases down the group

Lithium

Least reactive of first three alkali metals

Potassium

Most reactive of first three alkali metals

Group 7

Halogens with 7 outer electrons

Halogens

Reactive non-metals forming diatomic molecules

Group 7 with metals

Forms salts

Group 7 with non-metals

Forms covalent compounds

Group 7 melting and boiling points

Increase down the group

Group 7 reactivity

Decreases down the group

Displacement reaction

More reactive halogen displaces less reactive halogen from solution