1. Chapter 7 and 8

2.  Valence electrons are responsible for the bonding between two atoms.

3.  In forming compounds, atoms tend to achieve the electron configuration of a noble gas.  An octet is the set of eight electrons in the outermost energy level

4.  Atoms of metals tend to lose their valence electrons, leaving a complete octet in the next lowest energy level.  Atoms of some nonmetals tend to gain electrons or share electrons with another nonmetal to achieve a complete octet.  The ions that are produced when atoms of chlorine and other halogens gain electrons are called halides.

5.  Ionic compounds are usually composed of a metal cation and a nonmetal anion.  Although they are composed of ions, ionic compounds are electrically neutral.

6.  Cations and anions have opposite charges and attract one another by means of electrostatic forces. The electrostatic forces that hold ions together in ionic compounds are called ionic bonds.

7.  A chemical formula shows the kinds and numbers of atoms in the smallest representative unit for a substance  A formula unit is the lowest whole number ratio of ions in an ionic compound  Ex. NaCl 1:1  Ex. MgCl 2 1:2

8.  Most ionic compounds are crystalline solids at room temperature  Dissolve in water (soluble)  Ionic compounds generally have high melting points  Ionic compounds can conduct an electric current when melted or dissolved in water

9.  The valence electrons of metal atoms can be modeled as a sea of electrons  Metallic bonds consist of the attraction of the free-floating electrons for the positively charged metal ions.

10.  Molecules and Molecular Compounds  A covalent bond is described as the sharing of electrons between two atoms. Covalent compounds are a combination of two or more nonmetals

11.  A molecule is a neutral group of atoms joined together by covalent bonds.  A diatomic molecule is a molecule consisting of two atoms of the same element.  Br I N Cl H O F

12.  Molecular Compounds tend to have relatively lower melting and boiling points than ionic compounds  Typically do not dissolve well in water  Do not conduct electricity when dissolved in water

13.  A molecular formula is the chemical formula of a molecular compound  A molecular formula shows how many atoms of each element a molecule contains.

14.  In covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases.  Single Covalent bond: Sharing of one pair of electrons  Double Covalent bond: Sharing of two pairs of electrons  Triple Covalent bond: Sharing of three pairs of electrons

15.  A coordinate covalent bond occurs when one atom provides the shared electron pair  Ex. Carbon Monoxide

16.  1. SUM THE VALENCE ELECTRONS FROM ALL ATOMS  2. Use the first atom of the chemical formula as the central atom (except hydrogen) and connect all other elements to that central atom with a single bond (---).  3. Complete the octets of the atoms bonded to the central atom. (Don’t forget that hydrogen only needs two electrons)  4. If there are not enough electrons to give the central atom an octet, try multiple bonds!.

17. H2OH2O  CF 4  CO 2

18.  Nonpolar covalent bond  Atoms in the bond pull equally  Bonding electrons are shared equally  Ex. Diatomic molecules

19.  Polar Covalent bond  Atoms in the bond pull with different strengths  Bonding electrons are not shared equally  Ex. HF

20.  Bond Polarity is based on the difference between two atoms electronegativity values  Remember that electronegativity is the ability of an atom to attract electrons in a chemical bond.