Aim: What are the Properties of Groups and how does the atomic radius change across a period and down a group ? Do Now: 1. Take out your periodic tables. 2. Come to the front of the desk and pick out your colored pencils/crayons.

Periodic Trends  Many trends of elements can be explained by electron configuration and position on the periodic table  Trends to be examined  Atomic radius  Ionic radius  Ionization energy  electronegativity

Atomic Radius  The distance from the center of the nucleus to the outermost shell.  Table S has the atomic radii values.

Atomic Radius- Down a Group: A Closer Look at Lithium and Sodium As you move down a group or family the atomic radius increases due to more energy levels.

Atomic Radius – Across a Period Same number of energy levels, but Be has more protons pulling on the outer electrons, making Be smaller. As you move across a period, the atomic radius becomes smaller due to increasing # of protons.

Which has the largest atomic radius?  Chlorine  Fluorine  Iodine  Bromine

Ions  An ion is an atom that has gained or lost electrons to have a full outer shell (8 electrons) like the noble gases.

Ions cont.  Atoms that gain electron(s) are called an anions, and have an overall negative charge. ClCl - atomanion  Atoms that lose electron(s) are called cations, and have an overall positive charge. NaNa + atom cation

Ionic Radius  The distance from the nucleus to the outermost electron of an ion.

Ionic Radius Sodium – Atom Sodium - Ion

Ionic Radius  The sodium ion loses the outer most electron to have a full outer shell. The ion is now smaller than the atom. It has one less electron making it have a +1 charge.

Ionic Radius  Metals tend to lose electrons (form cations) while nonmetals tend to gain electrons (form anions).  Metal ions are smaller than their atoms; nonmetal ions are larger than their atoms.

For each set of elements select the one with the smallest radius and give a reason for your choice.  Set 1: C, N, O, F  Set 2: F, CL, Br, I  Set 3: Na, K, Na +, K +  Set 4: Na +, K +, Mg 2+, Ca 2+  Set 5: F, F -, Na, Na +