1. Aim: What are the Properties of Groups and how does the atomic radius change across a period and down a group?
Do Now: Answer in your notebook
Explain in terms of valence electrons why the noble gases are unreactive.

2. 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

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

4. Atomic Radius- Down a Group: A Closer Look at Lithium and Sodium
Atomic radius increases down a group due to more energy levels

5. Atomic Radius – Across a Period
Same number of energy levels, but Be has more protons pulling on the outer electrons, making Be smaller. Atomic radius decreases across a period due to more protons.

8. Which has the largest atomic radius?
Chlorine
Fluorine
Iodine
Bromine

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

10. Ions cont. Atoms that gain electron(s) form a negatively charged ion.
Cl Cl-1
chlrorine atom chloride ion
Atoms that lose electron(s) form a positively charged ion.
Na Na+1
sodium atom sodium ion

11. How to find the charge of an ion?
Add charges from protons and charges from electrons.
Example 1: What is the charge of an ion that has 11 protons, 11 neutrons, and 10 electrons?
(+11) + (-10) = +1
Example 2: What is the charge of an ion that has 7 protons, 7 neutrons, and 8 electrons?
(+7) + (-8) = -1

12. What does the charge of ion mean?
(+1) lost 1 electron
(+2) lost 2 electrons
(+3 ) lost 3 electrons and so forth
(-1) gained 1 electron
(-2) gained 2 electrons
(-3) gained 3 electrons and so forth

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

14. Oxidation number and ionic charge
We will be using the oxidation numbers from the periodic table to tell us if an atom has lost or gained an electron(s) to form an ion.

15. Ionic Radius Sodium – Atom Na Sodium – Ion Na+1 2-8-1
2-8 (no electrons in 3rd shell)

16. 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.

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

19. 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+, Mg2+, Ca2+
Set 5: F, F-, Na, Na+