Periodic Trends

Note Guide

How is the periodic table arranged?

The modern periodic table is arranged by increasing atomic number (protons).

Classes of elements

Metals 80% of the table!

Solids at room temperature (except for Mercury)

Nonmetals Most are gases (except for Sulfur, Phosphorus,

Bromine)

Metalloids Similar properties to both metals and nonmetals

depending on the conditions

Periods and Groups

The vertical columns are called groups

The horizontal rows are called periods

The Representative Elements

Groups 1A – 7A For these elements

the group number represents the number of electrons in the highest occupied energy

level

Periodic Trends

Atomic size (Distance between nuclei) Increases from top

to bottom (energy levels increase)

Decreases from left to right (electrons get pulled closer to the nucleus)

Periodic Trends

Ionization energy (energy required to remove one electron)

Decrease from top to bottom

Increases from left to right (more attraction to nucleus makes it harder to get that electron out!)

Periodic Trends

_Ionic Size (size of a charged atom) Cations (+) are

always smaller than the atom from which they form

Anions (-) are always larger than the atoms from which they form

Increases from top to bottom

Decreases from left to right

Periodic Trends Electronegativity (ability of an atom to attract electrons

when in a compound)

Decreases from top to bottom

Increases from left to right

Vocabulary Cards

Periodic Table Metal Nonmetal Metalloid Energy Level Ionization Energy Cation Anion Electronegativity Valence Electrons

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