Chapter 5

 Electrons are located around the nucleus in the electron cloud.  The cloud is arranged into levels called shells or energy levels.  The elements in a period have the same number of levels or shells.

 Remember from Chapter 4- each column is called a group.  Each element in a group has the same number of electrons in their outer orbital, or “shell”.  Each shell can hold a specific number of electrons  1 st = 2 electrons  2 nd = 8 electrons  3 rd = 8 electrons  A shell must be filled before moving to the next level  The electrons in the outer shell are called “valence electrons”

Except for He, it has 2 electrons

 The goal of an atom is to be “happy.”  An atom is happy when it has a full outer energy level

A.B.

C.D.C.D.

E. F.

Step 1: Write down Element symbol Step 2: Find out how many valence electrons there are Step 3: Place electrons around the symbol one at a time and if there is enough double up O= 6 ValenceElectrons

1.Sodium Na 1 valence electron 2. Argon Ar 8 valence electrons

Use your periodic table to find the number of valence electrons for each of the following. Then, draw an Electron Dot Diagram for each. 1. Carbon 2. Lithium 3. Krypton 4. Boron 5. Neon 6. Nitrogen 7. Flourine 8. Helium 9. Aluminum 10. Calcium

 Chemical Bonding- combining of atoms to form molecules or ionic compounds  Chemical Bond- what holds the atoms together

 Remember from last week, the periodic table tells you how many valence electrons an atom has.  If we know the number of valence electrons, we can figure out which atoms combine and how.

 All have 8 valence electrons except Helium which has 2  All of these atoms are happy because their outer shell is full.  Since they are happy, they are not likely to form compounds.

 Ionic- between metal/nonmetal  Covalent- between nonmetals  Metallic- between metals

 Ionic Bonding- bond that forms when electrons are transferred from one atom to another  Ions- charged particles that form when an atom gains or loses electrons  This occurs between a metal and a nonmetal  Polyatomic ion- ionic bond with more than one bond  NaOH and NO 3

What is the element for A? How many valence electrons are missing from A to make it happy? Is it easier to gain 5 electrons or lose 3 electrons? What is the name for B? A B.

If you lose electrons, the charge becomes a positive If you gain electrons, the charge becomes a negative

 Positive charges bond with negative charges  Positive always is written first  You may have to increase the number of atoms to balance the bond

 Using 2 different colors, draw the electron dot diagram for each atom  Decide whether each will gain or lose electrons  Draw arrows to show where the electrons are transferred  Write in the new charge for each molecule

 Bond Sodium(Na) with Fluorine(F).  Bond Beryllium(Be) with Oxygen(O).  Bond Aluminum(Al) with Phosphorus(P).  Bond Magnesium(Mg) with Sulfur(S).

 Good when charges are not equal  Bond Aluminum with sulfur  Top number loses charge and goes to bottom number  Al +3 S -2  Al 2 S 3  Answer=Al 2 S 3

 Bond Fluorine with Boron  Bond Aluminum with Selenium  Bond Chlorine with Gallium  Bond Silicon with Sulfur.

 Covalent bond- formed when atoms share one or more pairs of electrons these form molecules Shared Electrons HH

 Polar bonds- electrons are shared unequally  Nonpolar bonds- electrons are shared equally

H2OH2O

 Draw the EDD for all elements  Look for ways to make the “puzzle pieces” fit together  If two elements are sharing an electron it will be on the same side

 B +3 O -2  B 2 O 3 charge TOP how many BOTTOM

 NH 3  H 2 S  CH 4  Cl 2  CO 2

Metallic bond- attraction between a positive metal ion and the electrons surrounding it Alloy- has two or more metals that are bonding together

▪ Resist rust ▪ Ductile-put into a wire ▪ Malleable- flattened into sheets

 Low melting points  Poor conductivity  Do not break up into ions

 Forms ionic crystals  Has high melting points  Bonds are broken by electricity

 H2  F2  H2O  N2  NH3  CH4  CO2  C2H 6  O2  Br2  PCl3  SiO2  C2H4  Cl2  C2H2  I2