lecture2

Atomic number z number of protons determines the

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Unformatted text preview: tons. Determines the chemical identity of the atom. Mass Number (A) - total number of protons and neutrons in nucleus. Isotopes - elements of the same atom with different mass numbers. (Gr. occupying the same space) mass numberÆ A atomic numberÆ Z X ¨ symbol 1 2 3 12 examples: 1 H, 1 H, 1 H 6 13 14 C, 6 C, 6 C 234 U (0.005%), 235U (0.720%), 238U (99.275%) 17 8 2- O has 8 protons, 9 neutrons and 10 electrons 2.6 Molecules and Ions Molecule - cluster of 2 or more atoms held together by covalent bonds Covalent bond - chemical bond caused by sharing electrons The atoms can be the same O2 or different H2O formulas: HH || H–C–C–H || HH structural formula molecular formula C2H6 empirical formula CH3 CH3CH2OH and CH3OCH3 have the same molecular formula but different structural formulas. Sometimes condensed structural formulas are used. Ion - atom or cluster of atoms with charge Cation - ion with positive charge (lost electrons) Anion - ion with negative charge (extra electrons) + - Na Na + e - Cl + e- Æ Cl + - Na + Cl Æ NaCl Ionic bond - chemical bond caused by electrostatic attraction between oppositely charged ions Ionic compounds have high melting points but melt to form conductive liquids. Molecular compounds usually have low...
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This note was uploaded on 04/05/2014 for the course CHEM 1211 taught by Professor Jackduff during the Spring '13 term at SPSU.

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