7.2 How are Lewis symbols written? The symbol of an element surrounded by dots, where the number of dots is equal to the number of valence electrons. Dots are spread out on four sides of the symbol. Why do Be, B, and C have 2, 3, and 4 unpaired electron's according to their Lewis structure, but not according to their electron configurations? Because, when bonding, they act as if they have 2, 3 and 4 unpaired electrons. This is also true of other elements in the same groups as Be, B, and C. What is a quick way to check the number of valence electrons of a representative element? Look at the group number of the element. For example, O is in group VI (roman numeral 6) and has 6 valence electrons. How can the reaction of Na with Cl be represented with Lewis symbols? How are molecular substances different from ionic ones? They do not benefit from a lattice energy. Instead, they form because of the lowering of energy that comes from sharing electrons. Between atoms in a molecule, which forces result in attraction and which result in repulsion? There is an attraction between the nucleus of one atom and the electrons of another. There is a repulsion between nuclei of opposite atoms and between electrons of opposite atoms. At what distance do atoms remain separated?
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This note was uploaded on 04/12/2011 for the course CHEM 1010 taught by Professor Marshall during the Spring '11 term at North Texas.