Periodic Table

The Periodic Table

The periodic table is used as a method of classifying and predicting the properties of elements.

Periodic Trends

Elements become more non-metallic across a period. Elements near the bottom left corner of the table are the most metallic while elements near the top right corner are the least metallic.

An element's group number is equal to the number of electrons in its outer shell (valence electrons). For example, oxygen is in group 6 and has 6 valence electrons.

Group Properties

Group I

This group, known as the alkali earth metals, is a series of soft metals that react vigorously with cold water to produce an alkali and hydrogen gas.

Going down the group:

reactivity increases
density increases
melting point decreases

Examples: lithium, sodium, and potassium

Group VII

Group VII, otherwise known as Group 17, are the halogens. These are a series of non-metals that form diatomic molecules.

Going down the group:

reactivity decreases
density increases
boiling point increases
color darkens

Examples: fluorine, chlorine, bromine, and iodine

Transition Elements

The transition elements are metals that:

have high melting points
have high densities
form colored compounds
show catalytic activity
have variable oxidation numbers

Examples: iron, cobalt, nickel, and copper

Group VIII

Group VIII, otherwise known as Group 18, are the noble gases. These are a series of monatomic gases which are chemically inert (unreactive). These gases are unreactive because their valence (outer) shell is full. This means that they rarely form compounds.

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Group VIII is also sometimes called Group 0.