 What is the electron configuration for Magnesium? What block, group and period does it belong to?  What is the noble gas configuration for Iodine? Is it a metal, nonmetal or metalloid?  Draw an orbital diagram for Magnesium and Iodine.

 Chemical compounds form because electrons are lost, gained or shared between atoms.  The electrons that interact in this manner are those in the highest energy levels.  The electrons available to be lost, gained or shared in the formation of chemical compounds are referred to as valence electrons.

 Atoms gain or lose electrons to have the same number of electrons as noble gases!  Board game analogy 1. Identify the element on the periodic table 2. Find the closest noble gas

3a. If the closest noble gas is to the right (a higher atomic number) The element gains electrons The element will become negatively charged --Anion 3b. If the closest noble gas is to the left (a lower atomic number) The element loses electrons The element will become positively charged--Cation

 What ion would chlorine form?  Ar is the closest noble gas  Cl will gain one electron to have the same number of electrons as Ar  Cl has one more electron than protons  The charge of a chlorine ion is -1  You would write it as Cl -1 or Cl 1-

 What ion would calcium form?  Ar is the closest noble gas.  Ca will lose two electron to have the same number of electrons as Ar.  Ca has two less electron than protons (Or two more protons than electrons)  The charge of a calcium ion is +2  You would write it as Ca +2 or Ca 2+

 Br  S  N  Mg  K  Al Br -1 Anion S -2 Anion N -3 Anion Mg +2 Cation K +1 Cation Al +3 Cation

 Br 1-  S 2-  N 3-  Mg 2+  K 1+  Al 3+

Atomic Radius: one-half the distance between the nuclei of identical atoms that are bonded together.

Atomic Radii Trends Atoms tend to be smaller the farther to the right they are found across a period. WHY? The trend to smaller atoms across a period is caused by the increasing positive charge of the nucleus, which attracts electrons toward the nucleus. Atoms tend to be larger the farther down in a group they are found. WHY? The trend to larger atoms down a group is caused by the increasing size of the electron cloud around an atom as the number electron sublevels increases. Shielding—the repulsion of more electrons negates the nuclear charge attracting the electrons inward.

Ionization Energy The energy required to remove one electron from a neutral atom of an element is the ionization energy, IE (or first ionization energy, IE 1 ).

Ionization Energy Ionization energies increase across each period. This increase is caused by increasing nuclear charge. A higher charge more strongly attracts electrons in the same energy level. Ionization energies decrease down the groups. Electrons removed from atoms of each succeeding element in a group are in higher energy levels, farther from the nucleus. The electrons are removed more easily. Dog walking analogy

Ionic Radii A positive ion is known as a cation Formed by loss of electrons electron cloud becomes smaller than neutral atoms As you move across a period the cation size decreases A negative ion is known as an anion Formed by gain of electrons Electron cloud becomes larger than neutral atoms As you move across a period the anion size decreases

Electronegativity The tendency for the atom to attract electrons when chemically combined with atoms of another element. Electronegativities tend to increase across periods, and decrease or remain about the same down a group.

 Page 167 #27, 28, 29, All  Finish Ion Configuration Worksheet