1. Periodicity Objectives:
AHSGE Reading Discern organizational patterns.
Other AOD C.3.2 Recognize periodic trends of elements, including the number of valence electrons, atomic size, and reactivity.
Periodicity

3. Periodic Law
Dmitri Mendeleev’s periodic table had the elements arranged in order of increasing mass.
There is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number

4. Modern Periodic Table What are the columns called? Answer: Groups
What are the horizontal rows called?
Answer: Periods
Label groups & rows on your periodic table!!

5. Modern Periodic Table
Representative elements: elements in the A groups (1A-8A)
“the main group”
Possess a wide range of physical and chemical properties
Transition elements: elements in the B groups (1B-8B)

6. Metals Describe some properties of metals. Metals:
Generally shiny
Most are solid at room temperature
Good conductors of heat and electricity
Ductile and malleable
Most group A and all group B elements are metals.

7. Groups 1A and 2A, EXCEPT HYROGEN, are metals.
The other elements in group 1A are called alkali metals.
Reactive & Readily combine with group 6 and 7 elements.
Group 2A elements are alkaline earth metals.
Contain a pair of electrons in their outermost shell.

8. Both groups 1A and 2A are highly reactive (1A more so).
Why would group 1A be more reactive than group 2A?
Answer: Group 2A has a FILLED s orbital, but group 1A’s s orbital is only half-filled, so that electron is still looking for a partner to hook up with.

9. Group B elements:
Transition metals: located on the main body of the periodic table
Inner transition metals: the 2 rows located along the bottom of the periodic table

10. Nonmetals Describe some properties of nonmetals. Nonmetals:
Generally gases or brittle, dull-looking solids
Poor conductors of heat or electricity
The ONLY nonmetal that is a liquid at room temperature is bromine.
Located in the upper right portion of the periodic table

11. Halogens: Group 7A elements; highly reactive
Noble gases: Group 8A; extremely Unreactive.
Why are group 8A elements unreactive?
Answer: Their outer valence shell is filled, so they have no need to pair up with anyone else.

12. Metalloids Have properties of both metals and nonmetals.
Stair-step down from boron to astatine and germanium to polonium.
They separate the metals and nonmetals on the periodic table.

13. Assignment Label the following on your blank periodic table:
Groups & periods
Representative elements
Transition elements
Metals: alkali metals, alkaline earth metals, transition metals, and inner transition metals
Nonmetals
Halogens
Noble gases
metalloids