Atoms - Bond is union b/w electrons in outer shell of atoms...

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Atoms, Molecules, and Life CH. 2 8-31-09 What are Atoms? Fig. 2-1 Basic structural unit of matter (i.e. smallest pieces of stuff) o Protons- Positive charge o Electrons- negative charge o Neutrons- no charge Elements differ in # of protons (fig. 2-2) Has specific physical and chemical properties Can’t be broken down by chemical rxn’s Atomic mass = # of protons and neutrons Building-Up Principle Electrons fill the shell closest to the nucleus, then occupy the next shell o 1 st shell- 2 electrons o 2 nd shell- 8 electrons o 3 rd shell- 8 electrons o Example: Atomic # of Carbon is 6, 2 in 1 st shell 4 in 2 nd shell Isotopes Atomic mass = # of protons and neutrons Isotopes vary in number of neutrons Ions Ions are atoms that vary in the # of electrons in outer shell Atoms are most stable when outer electron shell is full
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Extra electrons = negative charge Fewer electrons create a positive charge Chemical Bonds, Molecules, and Compounds
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Unformatted text preview: Bond is union b/w electrons in outer shell of atoms Atoms bond to form molecules Molecules may contain atoms of only one element O2 Molecules of compounds contain more thatn one element H2O Important Bonds in Biological Molecules Ionic Bonds o Attraction between Ions Sodium has 1 electron in outer shell: chlorine has 7 Sodium can lose 1 and chlorine can gain it Sodium becomes a + ion Chlorine becomes a - ion Covalent Bonds o Atoms share a pair or pairs of electrons to fill outermost shell Single covalent bond Plus 1 pair electrons Double covalent bond Plus 2 pairs Triple plus 3 o Nonpolar if atoms share electrons equally Hydrogen gas (H-H) o Polar if electrons spend more time orbiting one atom and less around another Fig. 2-4 Hydrogen Bonds...
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Atoms - Bond is union b/w electrons in outer shell of atoms...

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