1. Bonding

2. Formulas  Chemical formulas Chemical formulas  Tell us what elements a compound contains and the exact number of the atoms of each element in a unit of that compound  Examples:  SiO 2  1 atom of Silicon  2 atoms of Oxygen  CH 3 COOH  2 atoms of Carbon  4 atoms of Oxygen  2 atoms of Oxygen

3. How do you know how many dots to make?  Group 1 – 1 outer electron  Group 2 – 2 outer electrons  Group 3 – 12 – varies  Group 13 – 3 outer electrons  Group 14 – 4 outer electrons  Group 15 – 5 outer electrons  Group 16 – 6 outer electrons  Group 17 – 7 outer electrons  Group 18 – 8 outer electrons

4. Chemical Stability  An atom is chemically stable when its outer energy level is complete.  Atoms need 8 electrons to become stable.  Exception – Hydrogen and Helium need only 2 electrons.  Noble gases  Stable since they have a complete outer energy level

5. Chemical Bonding  Atoms with partially stable outer energy levels can gain, lose, or share electrons to obtain a stable outer energy level.  They combine with other partially stable outer energy levels to get 8 electrons  They become stable.  An attraction forms between the atoms, pulling them together to form compounds  Chemical bonds – the force that holds atoms together in a compound

6. Ions  Atoms lose or gain electrons which are called ions.  Ion  Charged particle since it has more or fewer electrons than protons  Loss of electrons – more protons  Called cations  Gain of electrons – less protons  Called anions

7. Ions GroupValence Electrons Electrons Lost or GainedNumber of Electrons Lost or Gained Oxidation Number Group 11Lose1+1 Group 22Lose2+2 Group 133Lose3+3 Group 144Lose – Tin, Lead Gain/Share – Carbon, Silicon, 4+4 -4 Group 155Gain/Share3-3 Group 166Gain/Share2-2 Group 177Gain/Share1 Group 188Stable00

8. Ionic Bonding – The Givers and Takers  Transfer of electrons between a metal and a nonmetal  Metals – lose electrons and become a positive ion  Nonmetals – gain electrons and become a negative ion  The positive charge of the metal and the negative charge of the atom must be balanced.  The compound is neutral.

10. Covalent Bonding – The Happy Couple  The sharing of electrons between two nonmetals  This sharing of electrons is called covalent bonding.  Types of bonds  Single bond – 2 shared electrons or 1 pair of electrons between atoms  Double bond – 4 shared electrons or 2 pairs of electrons between atoms  Triple bond – 6 shared electrons or 3 pairs of electrons between atoms

12. Metallic Bonding – “Sea of Electrons”  The positively charged metallic ions are surrounded by a cloud of electrons  Metallic ions are positively charged since metals tend to lose electrons.  Electrons move freely among the positively charged ions

14. Unequal Sharing  Electrons are not always shared equally between atoms in a covalent bond.  Strength of the attraction is related to  the size of the atom  the charge of the nucleus  the total number of electrons the atom has  Electrons that are unequally shared are held more closely to the atoms with the larger nucleus.