Electron Configuration and Periodic Properties/Trends Chapter 5 Section 3 Pgs. 140-154

There is a correlation between the arrangement of elements in the periodic table and their electron configuration

This P.T. is color coded by main energy level…

Concepts to know about… Atomic radius Ionization energy Electronegativity Valence electron Be able to compare periodic trends of main group elements and explain why these trends occur “Main” group elements do not include the transition metals or rare Earth metals.

Atomic Radius… One half of the distance between two nuclei of the identical atoms that are bonded together

Atomic radius trends… Across Periods… Down Groups/Families... Smaller atoms across a period (left to right) Caused by increasing positive charge of the nucleus pulling in the electrons Down Groups/Families... Atoms increase in size down a group/family because higher main energy levels are being filled as you down a group

Ions... Ions are… A single atom or a group of bonded atoms that have an overall positive or negative charge Na+ Cl- Cr3+ Polyatomic ions: OH- CO32- CN- Ionization is any process that results in the formation of an ion How do ions form??? Loss or gain of electrons!!!

Ions... Cation = positive ion = electrons have been removed Anion = negative ion = electrons have been added

Ionization energy... Energy needed to remove one electron from a neutral atom is the first ionization energy ( symbolized as IE1 ) Second ionization energy, third ionization energy remove electrons from an ion too. Second ionization energy is always larger than first. Third larger than second…

Ionization energy trends… Across Periods… Ionization energy increases across a period due to increases nuclear charge (# of protons w/in nucleus) If electrons are closer to the nucleus they are harder to remove away... Down Groups Decreases down a group because the higher main energy levels are further from nucleus Electrons that are farther away from nucleus can be removed more easily...

Ionization energy Trends

Valence Electrons… Valence Electrons are available to be lost, gained or shared when forming chemical compounds Valence electrons are the electrons found in the outermost S and P orbitals only!! there are always a maximum of 8 v.e. (S holds 2 and P holds 6)

Atoms in the same columns have the same number of valence electrons. Helium only has 2 valence electrons (not 8 like the rest of the noble gases) 8 1 2 3 4 5 6 7

Electronegativity… Is a measure of the ability of an atom in a chemical compound to attract electrons Essentially to pull electrons away from the other atom(s) Valence electrons hold compounds together Uneven electrical charge is important in compound formation and other chemical properties

Electronegativity Across Periods… Down Groups/Families Increases across periods Fluorine is the most electronegative Down Groups/Families Decreases or stay same down a group Noble gases do not form compounds so are not assigned electronegativity numbers

Electronegativity Trends