Do Now Why Do Atoms Bonds with each other? Bonding and Stability An atom becomes more stable when it acquires the electron configuration of a noble gas Two for the 1st principal energy level and eight for the others. The Octate Rule As any system become more stable, its energy decreases IONIC BONDING IONIC BONDING To achieve noble gas configuration, a pair of atoms may fill their valence level by transferring electrons between them to form ions with opposite charges. The opposite charges cause them to attract strongly, forming this type of bond. IONIC BONDING The attraction is not limited to pairs of ions. Oppositely charged ions arrange themselves in a regular array. The formula tells us the ratio of positive to negative ions- The Formula Unit. Eg. In the case of NaCl, the ratio is 1 to 1 IONIC BONDING What is necessary for electron transfer to occur? One atom must be Low able to lose electron readily Ionization Energy The other atom must be able to Negative gain electrons readily Electron Affinity COVALENT BONDING COVALENT BONDING Some pairs of atoms do not have a strong tendency to transfer electrons between them. These atoms SHARE electrons between them. Two atoms may normally share one, two, or three pairs of electrons. The atoms bond together because the shared pair or pairs belonging to both atoms COVALENT BONDING Single Covalent bond Each molecule a single pair of electrons is shared between the atoms. F—F and H--Cl COVALENT BONDING The sharing of the electrons is not always equal between both atoms. Nonpolar Polar Covalent Covalent The electron pair is not The pair of shared equally; the electrons is chlorine atom has a shared equally greater attraction for the by both atoms shared electrons than the hydrogen atom. F--F H--Cl Multiple Covalent Bonds Create the electron dot symbol for oxygen. Construct a molecule of O2. In order to place eight electrons in the valence level of each oxygen atom it is necessary that the atom share two pairs of electrons This is known as double covalent bonds. Multiple Covalent Bonds How is a molecule of N2 constructed? Nitrogen has five valence electrons It is necessary that the two atoms share three pairs of electrons This is known as a triple covalent bond. Coordinate Covalent Bonding Draw the Lewis structure for NH3. Add a H+ ion to form the ammonium ion (NH4+) The hydrogen ion lacks electrons; and when it bonds the nitrogen atom must contribute both electrons to the shared pair. This type of bond is found in many molecules and polyatomic ions.