Periodic Law The periodic law states that physical and chemical properties of the elements are periodic functions of their atomic numbers In other words, when the elements are arranged by their atomic numbers you should see chemical and physical properties repeating themselves

Parts of the Periodic Table

Names of different sections Main group elements- groups 1, 2 , 13-18 Alkali Metals- first column (Group 1) excluding H Alkaline Earth Metals-Group 2 Transition Metals- groups 3-12 Halogens- Group 17 Noble Gases- Group 18 Lanthanide Series Top row on the bottom two Actinide Series bottom row of the bottom two Lanthanide and Actinides fit into the table above

Transition Metals Halogens Alkaline Earth Metals Noble Gases Alkali Metals Halogens Alkaline Earth Metals Lanthanide Series Actinide Series

Families Have similar properties Noble Gases are extremely inactive or inert (doesn’t like to react w/ anything) That is because they have a full valence shell (the state everything wants to be in) Halogens are extremely reactive Alkali metals are extremely reactive Transition metals are slightly reactive

Periodic Table Key Always pay attention to the key of a periodic table because everyone looks slightly different 3 things will always be in a square (some tables have much more) 1-     atomic number 2-     chemical symbol 3-     atomic mass 13 Al 26.981539

Metals and nonmetals

Metals vs. Nonmetals Use the steps on the periodic table to determine what type of element it is. Left of the steps are metals (Except H) Right of the steps are nonmetals Elements on the steps are metalloids or semiconductors (except Al-it is a metal)

Metals Physical properties- luster, conductive, malleable, ductile, high density, high melting point All except Hg are solids at room temperature Chemical properties- most metal will react with O2 or H2O to form an oxide (metal + Oxygen), This is rusting or tarnishing. When this compound rubs off the surface of the elemental metal it is called corrosion Metals give up e- to get to a full valence shell

Hydrogen Hydrogen fits into its own group and is not an alkali metal or even a metal This is because it is only 1 proton and 1 electron (no neutrons) although under the extreme pressure on Jupiter it may act like a metal

Nonmetals Physical properties- dull, don’t conduct, brittle, low density, low melting points Can be solid, liquid or gas at room temperature depending on the element Nonmetals take e- to get a full valence shell

Metalloids (semiconductors) can be shiny or dull, conduct ok, ductile and malleable or brittle These elements have become really important because of the computer revolution Computer chips are made out of semiconductors (normally Si) by position Al is a metalloid, but its properties make it a light metal

What causes reactivity of elements All atoms want to have a completely full valence shell (normally 8 electrons). For the moment we will only concentrate on main group elements Noble gases are already full. Elements that are really close, desperately want to get there (halogens and alkali), and tend to be the most reactive.

Gaining electrons metals lose electrons, nonmetals gain electrons and metalloids can go either way is a loose rule. Obviously the quickest way for something that has more than 4 electrons to get to 8 is to gain electrons (through chemical bonds). halogens want to gain 1, oxygen group wants to gain 2, nitrogen group wants to gain 3.

Losing Electrons Metals will gain a full valence shell by losing electrons. (there is a full shell underneath unless it is hydrogen) alkali will lose 1 electron, alkaline earth will lose 2 etc.

Vocabulary Ion- charged atom or molecule Something becomes an ion by gaining or losing electrons (not protons) anion-negatively charged ion A Negative ION Caused by gaining electrons cation-positively charged ion ca+ion Caused by losing electrons

charges on groups Alkali metals want to lose 1 electron. alkali metals form ions with a +1 charge Write this as Na+ or K+ alkaline earth- Ca2+ Mg2+ halogens want to gain one electron Cl- or Br- oxygen group wants to gain 2 O2- or S2-

Common Ion Charges

Ions are completely different from the element of the same name Valence electrons are mainly responsible for chemical/physical properties. alkali metals are so reactive because they “want” to get rid of that electron. An ion is the element after it got rid of the electron. Therefore the atom is nowhere near as reactive as it used to be. This is like comparing the ashes from a stick of dynamite to the stick of dynamite.

So are ions like noble gases? No, ions are not the same as noble gases valence electrons are mainly responsible for chemical/physical properties but not solely responsible. Protons and neutrons still have a role. When K loses an electron or Cl gains an electron it has the same number of electrons as Ar, however protons and neutrons are different. so K+, Cl-, and Ar are different things, even though they have the same number of electrons.

charges also affect properties Ar is neutral so it would be unaffected by a positive or negative charge. Cl- is attracted to a positive charge and repelled by a negative charge. K+ would be attracted by a negative charge and repelled by a positive charge.