The Periodic Table

Valence electrons are the electrons that occupy the outside orbitals of the electron cloud.◦ The highest energy level is equal to the period

Valence Electrons

Group 1 has 1 valence electron Group 2 has 2 valence electrons Groups 3-12 (transition metals) vary Group 13 has 3 valence electrons Group 14 has 4 valence electrons Group 15 has 5 valence electrons Group 16 has 6 valence electrons Group 17 has 7 valence electrons Group 18 has 8 valence electrons

Valence Electrons

Ionization – The formation of an ion

Groups 1-14 elements make cations ◦ These ions ALWAYS have 0 valence electrons

Groups 14-17 elements make anions◦ These ions ALWAYS have 8 valence electrons

Group 18 elements (noble gases) don’t make ions because they already have 8 valence electrons

The charge of an ion can be determined from the number of valence electrons◦ 1 valence e- makes a +1 charge because it had to lose 1 electron to equal

zero◦ 6 valence e- makes a -2 charge because it had to gain 2 electrons to equal 8◦ 4 valence e- makes either a +4 or a -4 charge, depending on the element

Formation of Ions

Formation of Ions

Group 1 Alkali Metals: Most metallic and reactive group◦ form +1 cations

Group 2 Alkaline Earth metals: Very reactive group◦ form +2 cations

Block D Transition Metals: Semi-reactive◦ form cations with different charges

Block F Lanthanides and Actinides: Radioactive and extremely heavy metals

Group 16 Chalcogens: Very reactive and electronegative◦ form -2 anions

Group 17 Halogens: Extremely reactive and electronegative group◦ form -1 anions

Group 18 Noble Gases: Completely unreactive because of complete valence shell

Properties of Groups

There are 3 types of elements: metals, metalloids and nonmetals

◦ 1) S, D and F block Metals: Malleable (can change shape without breaking), shiny, conducts electricity

◦ 2) P Block Metalloids: Show both metallic and non-metallic character. Metalloids touch the staircase of the periodic table

 ◦ 3) P Block Nonmetals: dull, brittle, and poor at

conducting electricity because they hog electrons

Types of Elements

Mendeleev was the scientist responsible for seeing the pattern of properties of the elements in the periodic table

◦ he was the first to organize those elements into periods and groups.

◦ Elements within the same group have the same physical and chemical properties.

◦ When he organized his version of the table, there were holes in it because there were only 60 out of 110 known elements at the time. After he died, the holes were later filled by newly discovered elements, verifying what he knew to be correct:

you can predict how an atom will behave by knowing where its atomic number falls on the periodic table.

Periodic law – Both physical and chemical properties of the elements are functions of their atomic numbers.

History