chapter 6 sections 1,2 and 3. key terms only a few atoms exist as isolated atoms – noble gases ...
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Chapter 6Sections 1,2 and 3
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Key Terms Only a few atoms exist as isolated atoms – Noble Gases Molecule
Smallest electrically neutral unit of a substance that still has the properties of the substance.
Made up of two or more atoms that behave as a unit. Some are diatomic (appear as pairs)
Br2I2N2Cl2H2O2F2
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Molecular Compounds Atoms of different elements combine chemically Compounds composed of molecules are called
molecular compounds. Some general characteristics:
Low melting and boiling points Most are liquids or gases
Composed of two or more non-metals
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Ionic Compounds Ions – atoms or groups of atoms that have positive or
negative charges (that means the # of p+ does not equal the # of e-)
Metallic elements tend to form cations (positive charges) The protons outnumber the electrons
The charge is usually written after the symbol and to the upper right (Na+)
Cations are named the same as the element. Ions behave very differently than the atoms they came from.
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Anions Non-metals usually form anions. Negative (electrons outnumber the protons). Happens when elements gain electrons The name of a typical monatomic anion (1 atom that
is negative) ends in –ide
Example: Cl- = chloride
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Compounds composed of cations and anions are called ionic compounds. Usually made of metals with non-metals Ionic compounds are electrically neutral Usually solids at room temperature and melt at
extremely high temperatures.
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Chemical Formulas
Shows the kinds and number of atoms in the smallest representative unit of the substance.
Use elemental symbols Subscripts show haw many of each atom are
present. Example: oxygen = O2
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Molecular Formula
Chemical formula for a molecular compound. Tells nothing about structure or arrangement of
atoms. Example = carbon dioxide = CO2
One carbon atom and two oxygen atoms tightly bound to each other.
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Formula Unit Used for ionic compounds Ionic compounds are not molecules It is the lowest whole number ration of ions in a
compound. Example: NaCl (sodium chloride or table salt) is made of one
sodium ion and one chloride ion. Thus, the ratio is 1:1 (sodium = +1 charge and chloride = -1 charge)
Example #2: MgCl2 (magnesium chloride) is made of one magnesium cation (+2 charge) and two chloride anions (-1 each) thus the ratio is 1:2
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Laws Law of multiple proportions
If two or more compounds made of the same elements exist they are a whole ratio of each others composition.
Law of definite proportions Samples of the same compound have the elements
present in the same ratio.
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Monatomic Ions Ions consisting of only one atom Table 6.2 (p143) Can be predicted from group on the periodic table.
1A 2A 3A 4A 5A 6A 7A 8A
Li+ Be+2 N-3 O-2 F-
Na+ Mg+2 Al+3 P-3 S-2 Cl-
K+ Ca+2 As-3 Se-2 Br-
Rb+ Sr+2 I-
Cs+ Ba+2
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Transition Metals Most can have multiple charges
Exceptions = Silver (Ag+), Zinc (Zn+2) and Cadmium (Cd+2)
Roman Numeral is used to show the charge on the cation Example: Copper (I) = Cu+1
Roman Numeral is the charge!
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Table 6.3 Page 144
Formula Stock Name Classical Name
Cu+ Copper (I) Cuprous ion
Cu+2 Copper (II) Cupric ion
Fe+2 Iron (II) Ferrous ion
Fe+3 Iron (III) Ferric ion
Pb+2 Lead (II) Plumbous ion
Pb+4 Lead (IV) Plumbic ion
Sn+2 Tin (II) Stannous ion
Sn+4 Tin (IV) Stannic ion
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Polyatomic Ions Tightly bound groups of atoms that
behave as a unit and carry a charge. Change the prefix and suffix to show a
change in the number of oxygen present. Exceptions = Cyanide, Hydroxide and
ammonium Practice with the common ion sheet