1. Bellwork Question4-Style #4 1)Write a balanced net ionic equation for the reaction that occurs when sodium metal is added to pure water. a)How could you verify the identity of the gas evolved? b) What would be the pH of the resulting solution? Less than 7, near 7, or greater than 7?
4. Bonding always involves valence electrons which can be represented by Lewis dot symbols OCTET RULE- Atoms seek to gain a noble gas configuration, which is usually eight valence electrons. Remember Helium only has 2 valence electrons, so elements closest to He are most stable when they obtain 2 valence e - like H, Li, and Be. Hydrogen is also stable as a H + ion which has no electrons and is simply a proton + . Li 1 valence e - Be 2 valence e - B 3 valence e - C 4 valence e - N 5 valence e - O 6 valence e - F 7 valence e - Ne 8 valence e -
83. The stability of a molecule is related to the strength of the bonds in the molecule.
87. Bond enthalpies can be measured through the “enthalpy of atomization”, which measures the energy required to break a molecule into free gaseous atoms. D(C-H) = 1660kJ divided by 4 because there are 4 C-H bonds in methane.
89. Breaking bonds = endothermic energy must be provided to break a bond Bond formation = exothermic a stable bond is always lower energy than the non-bonded atoms
90. Molecules with strong (stable) bonds tend to be less reactive. Naturally abundant compounds are usually very stable with strong bonds. Ex. O=O is 495kJ/mol O-O is 146 kJ/mol O 2 is stable & abundant H 2 O 2 is not
98. The higher the bond order the shorter & stronger the bond Bond order = 1 Longest & weakest Bond order = 2 Med length & strength Bond order = 3 shortest & strongest