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 MetallicLess Metallic More Metallic Less 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 Li Be B B C C N N O O F F Ne More protons means outer electrons are pulled in closer! F F Cl Br I I At More energy levels means greater atomic size!

Atomic Radii General Trend Radius Increases Radius Decreases Radius decreases Radius increases

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

Electronegativity

Ionization Energy +