Periodic Properties

Chemical and physical properties of the elements change with their position

in the periodic table.

Review

• Group = column• Period = row• Octet Rule

– atoms tend to gain, lose, or share electrons in order to gain 8 valence electrons (full outer shell), like Noble gases

– An element with a full valence shell is a happy element

Atomic Size

Distance from the center of an atom's nucleus to the edge of its electron cloud.

atom

• Within a period, atoms generally get smaller as you move from left to right.

• WHY?Because of the increasing positive charge of the nucleus draws the electrons in more tightly.

Trend in Atomic Size

Trend In Atomic Size

• Within a group, atoms generally get larger as you move from top to bottom.

• WHY?Electrons are added to energy levels further from the nucleus.

Dr. Lanzaflame; Atomic radii; www.monroecc.edu/wusers/flanzafame/PerRadii.pdf

Ionization Energy

The amount of energy needed to remove one valence electron from an atom of an element.

 

• Within a period, IE increases as you move from left to right.

• WHY?– As you move from left to right the number of

protons is increasing thus increasing the coulombic attraction between the nucleus and the electrons.

Trend in Ionization Energy

Trend In Ionization Energy• Within a group, IE decreases as you

move from top to bottom.

• WHY?– The farther away from the nucleus an electron

is, the easier it is to remove because the coulombic attraction is less thus the positive charge of the proton has less hold on the negative charge of the electron.

Electronegativity

The ability to attract an electron from another atom.

• Within a period, EN increases as you move from left to right.

• WHY?

–The number of protons is increasing; therefore, the coulombic attraction is greater

Trend in Electronegativity

• Within a group, EN decreases as you move from top to bottom.

• WHY?–The atoms are larger due to

increased energy levels; therefore, the attraction for electrons would decrease

Trend in Electronegativity

Reactivity

Reactivity refers to how likely an atom is to react with other substances.

Trends in Reactivity• Metals

– Period - reactivity decreases as you go from left to right across a period.

– Group - reactivity increases as you go down a group

– Why? • To react, metals needs to get rid of

electrons, thus they need a low IE.

Trends in Reactivity• Non-metals

– Period - reactivity increases as you go from the left to the right across a period.

– Group - reactivity decreases as you go down the group.

– Why? • For nonmetals to react, they must gain

electrons, so they need a high EN.