Metallic Bonding The transition metals and Lanthanide/Actinide series hold their outermost electrons loosely This allows for metallic bonds – groups of metals held together in which their electrons are free to flow to different atoms

Electronegativity and Covalent bonds

Electronegativity An atom’s ability to attract another electron Electronegativity increases across a period It decreases down a group

Covalent bonds A bond in which two atoms are held together due to shared electrons

Single bond Double bond Triple bond One pair of electrons is shared Two pairs shared Triple bond Three pairs shared

Polarity When one element in a covalent bond has a higher electronegativity than the other, it holds the shared pair of electrons closer to its nucleus This side of the molecule becomes slightly negative, and the other side slightly positive This is known as polarity

The slightly charged ends of a polar molecule are known as dipoles The more electronegative side is called partially negative; the less electronegative side is called partially positive

Nonpolar covalent bonds When there are no partial charges, the bond is nonpolar Nonpolar covalent bond vs. nonpolar covalent molecule Some molecules are nonpolar because their partial positives cancel each other out

Hydrogen Bonds in water

Cohesion: Water molecules are attracted to other water molecules Adhesion: Water molecules are also attracted to other polar surfaces Capillary action: water moving up a thin tube against gravity

Surface Tension

Surface Tension

Rain drops Right (under ideal conditions) Wrong

Hydrophobic materials http://www.youtube.com/watch?v=LJtQ6dvcbOg http://www.youtube.com/watch?v=IfUaKXasdD4