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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
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
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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