1. Periodic Table

2. Dmitiri Mendeleev, 1871 Listed the elements in columns in order of increasing atomic mass.

3. Henry moseley, 1913 Determined the atomic number of the atoms of the elements. Arranged the elements in a table by atomic number. This is the way the periodic table is arranged today.

5. Metals metals  metalloids  nonmetals Properties of Metals: Luster Ductile Malleable Good conductors of heat and electricity, Lose electrons to form + ions Metals

6. Non-metals metals  metalloids  nonmetals Nonmetals Properties: dull brittle Insulators (poor conductors) gain electrons to form – ions Non-metals

7. Noble Gases are non- reactive, they have full electron shells

8. are periodic functions of the number of valence electrons an atom has. Groups or families (vertical column) - have similar chemical properties. Periods (horizontal rows) of elements usually start with a reactive solid and end with an unreactive gas, called a noble gas.

10. Valence Electrons: Electrons in the most outer ring of an element’s atom. Example: Group 1 all have one valence electron

12. 3Periodic Table Trends Patterns caused by the valence electrons on the periodic table.

13. Atomic Radius The size of an atom

15. Electronegativity: the ability of an atom to attract electrons

16. Ionization Energy Energy needed to remove one of atom’s electrons from its outermost shell high ionization energies = Stronger hold on electrons low ionization energies = weaker hold on electrons Losing an electron is called ionization