Adapted by Mrs. Hunt from Mrs. LaRosa www.middleschoolscience.com 2008 Introduction to the Periodic Table of Elements Adapted by Mrs. Hunt from Mrs. LaRosa www.middleschoolscience.com 2008 All images are from www.Chem4kids.com

OBJECTIVES What should you be able to do at the end of class? Describe the basic organization of the periodic table of elements. Use the periodic table to determine the number of electron shells and valence electrons of an element.

What is the Periodic Table of Elements? The Periodic Table of Elements is a way of organizing the elements in relation to each other so it is easy to find elements that have similar properties. Why is that helpful? It allows scientists to make predictions and explain events.

Periods Each row is called a “period” The elements in each period have the same number of electron shells 1st Period = 1 Shell 2nd Period = 2 Shells 3rd Period = 3 Shells 4th Period = 4 Shells Hint: A period comes at the end of a sentence--a horizontal line. www.chem4kids.com

Groups or Families 1 Group 8 = 8 electrons Group 1 = 1 electron Except for He, it has 2 electrons Group 2 = 2 electrons 1 18 Each column is called a “group” or family. 2 13 14 15 16 17 Each element in a group has the same number of electrons in its outer orbital, also known as its outer shell. 3 4 5 6 7 8 9 10 11 12 The electrons in the outer shell are called “valence electrons.” Hint: Your Family tree is vertical. www.chem4kids.com

Determine the number of shells and the number of valence electrons for: Carbon - C 2nd Period = 2 shells 14th Group = 4 valence electrons www.chem4kids.com

Determine the number of shells and the number of valence electrons for: Sodium - Na 3rd Period = 3 shells 1st Group = 1 valence electron www.chem4kids.com

Write your answers on your notes. Ne Name the element. Number of shells ? Valence electrons ?

Write your answers on your handout. Ne - Neon Name the element. Number of shells ? Valence electrons ? Neon 2nd Period = 2 shells 8th Group = 8 valence electrons 1

Created by G.Baker www.thesciencequeen.net Atom Models There are two models of the atoms we will be using in class. Bohr Model Lewis Dot Structure Created by G.Baker www.thesciencequeen.net

Created by G.Baker www.thesciencequeen.net Bohr Model The Bohr Model shows all of the particles in the atom. In the center are circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N. In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e. - + + - Created by G.Baker www.thesciencequeen.net

Electrons have special rules…. You can’t just shove all of the electrons into the first orbit of an electron. Electrons live in something called shells or energy levels. Only so many can be in any certain shell. The electrons in the outer most shell of any element are called valance electrons. Created by G.Baker www.thesciencequeen.net

Created by G.Baker www.thesciencequeen.net Nucleus 1st shell 2nd shell 3rd shell Adapted from http://www.sciencespot.net/Media/atomsfam.pdf Created by G.Baker www.thesciencequeen.net

Created by G.Baker www.thesciencequeen.net So let’s try it…. How to draw a Lithium atom First, look at the Periodic Table Second, determine the number of protons (Look @ the atomic number) Then determine the number of neutrons (Atomic mass – atomic number) Then determine the number of electrons (Look @ the atomic number) 3 Li Lithium 7 Created by G.Baker www.thesciencequeen.net

Created by G.Baker www.thesciencequeen.net So let’s try it…. Protons = 3 3 Li Lithium 7 - + + + - - Electrons = 3 2 in the 1st shell, 1 in the 2nd shell Neutrons = 4 (7-3=4) Created by G.Baker www.thesciencequeen.net

Created by G.Baker www.thesciencequeen.net Lewis Dot Structure The Lewis Dot Structure is a bit different from the Bohr model. It only shows the element symbol and it’s outer most electron shell. + - • O • • • • • Created by G.Baker www.thesciencequeen.net

Created by G.Baker www.thesciencequeen.net How to… Write the symbol. Start on the right hand side, working your way around the symbol. Try Lithium Created by G.Baker www.thesciencequeen.net

Draw both the Bohr Diagram & Lewis Dot Structure Name the element. Number of shells ? Valence electrons ?

Draw both the Bohr Diagram & Lewis Dot Structure Name the element. Number of shells ? Valence electrons ? Hydrogen 1st Period = 1 shell 1st Group = 1 valence electron

Draw both the Bohr Diagram & Lewis Dot Structure Be Name the element. Number of shells ? Valence electrons ?

Write your answers on your notes. Be Name the element. Number of shells ? Valence electrons ? Beryllium 2nd Period = 2 shells 2nd Group = 2 valence electrons

Draw both the Bohr Diagram & Lewis Dot Structure Name the element. Number of shells ? Valence electrons ?

Write your answers on your handout. Name the element. Number of shells ? Valence electrons ? Sulfur 3rd Period = 3 shells 6th Group = 6 valence electrons 1