Chemistry Review
Terms
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- Covalent bond
- formed by the sharing of electrons; electronegativity difference < 1.7
- Ionic bonds
- formed between metal and nonmetal; created by a transfer of electrons; electronegativity difference > 1.7
- Nonmetals
- tend to gain electrons and from negative ions (ions formed are larger than the neutral atoms: Ionic radii > atomic radii)
- Metals
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tend to lose electrons and form positive ions.
(Ions formed are smaller than the neutral atoms: Ionic radii < than atomic radii) - Diatomic molecules
- considered to have NONPOLAR covalent bonding. i.e. N2 à N=N
- Coordinate covalent bonds
- a covalent bond where both of the electrons are donated by one of the elements. Usually found in polyatomic ions.
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Periodic Table Trends
Trends - as you go from left to right across the table in a period -
Metallic character decreases
Atomic radius decreases [See Table P]
Ionization energy increases [See Table K]
Electronegativity increases [See Table K] - Metalloids
- have both metal and nonmetal properties. Contact the "staircase".
- Transition elements
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Produce COLORED SOLUTIONS.
found in the middle of periodic table - Empirical formula
- shows the simplest ratio of atoms in a molecule.
- Network solids
- held together by covalent bonds; high melting & boiling points. ; Extremely poor conductors of heat & electricity. i.e. SiO2, diamond - tetrahedral bonding (Cn), graphite (Cn) - hexagonal bonding