Review

The elements of the Periodic Table are arranged by: Periods – the number of energy levels. Groups – the number of valence electrons. Blocks – the orbital they are filling.

Atoms can gain or lose electrons.Metallic atoms lose e- and form cations.Nonmetallic atoms gain e- and form anions.

Metallicity

More Metallic Less Metallic

More M

etallicL

ess Metallic

Periodic Trends

Atomic Radius Ionic radius Ionization Energy Electronegativity

Atomic Radius

How big is an atom and why do we need to know?Atomic radius – distance from center of atom to its outer electrons.

Atomic radius has an affect on the chemical properties of an atom

Decreases going left to right in a period. More protons increases the pull on outer electrons

Increases going down in a group. More energy levels added makes the atom larger

The largest atom, therefore, is The smallest atom is

Francium.Helium

Atomic Radii in Period 2

LiLi BeBe BB CC NN OO FF NeNe

More protons means outer electrons are pulled in closer!

FF

ClCl

BrBr

II

AtAt

More energy levels means

greater atomic size!

Atomic Radii General Trend

Radius Increases

Radius Decreases

Rad

ius

decr

ease

s

Rad

ius

incr

ease

s

Ionic Radius

Ionic Radius – the distance from the center of an ion to its outermost electrons

In general, ionic radius follows the same trend as atomic radius

Cations are smaller than their atoms.– Losing electrons from outer shell makes them

smaller

Anions are larger than their atoms.– gaining electrons expands their outer shell

Ionization Energy

Ionization Energy – the energy required to remove 1 electron from an atom.

– Increases going left-to-right in a period• More protons increases attraction on outer electrons

– Decreases going down in a group• More energy levels make outer electrons harder to

hold

– The element with the highest ionization energy is Helium

Electronegativity

●Electronegativity (EN) – The ability of an atom to attract electrons in a chemical bond

● Increases going left-to-right in a period● More protons increases attraction for electrons of other elements

● Decreases going down in a group. ● More energy levels will shield electrons of other elements from the positive nucleus● Noble gases do not naturally form chemical bonds●The element with the highest Electronegativity is Fluorine

Review

● Atomic radius and ionic radius decrease left-to-right in a period● Ionization energy and Electronegativity increase left-to-right in a period

● The reason for these trends left-to-right is due to increasing number of protons,

● additional protons pull outer electrons in closer● Atomic radius and ionic radius increase going down a group● Ionization energy and electronegativity decrease going down a group

● the reason for these trends top-to-bottom is due to increasing energy levels, or layers, of electrons

● additional layers increase the atomic size, and shield the outer electrons from the positive nucleus