# Aim: What are the Properties of Groups and how does the atomic radius change across a period and down a group ? DO Now: 1. Write down the electron configuration.

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Aim: What are the Properties of Groups and how does the atomic radius change across a period and down a group ? DO Now: 1. Write down the electron configuration and the number of protons for Li, Na and Be. 2. Compare the atomic radii of Li and Na, and Li and Be. Which would have a larger atomic radius?

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.

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.

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

Ionic Radius  The distance from the nucleus to the outermost electron of an ion.  An ion is an atom that has gained or lost electrons to have a full outer shell (8 electrons) like the noble gases.

Ionic Radius Sodium – Atom Sodium - Ion

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

Ionic Radius  Some atoms gain electrons to have a full outer shell. The atom then takes on a negative charge and the ion is larger than the atom.  Metals tend to lose electrons while nonmetals tend to gain electrons.

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 +

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