Physical Science

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Physical Science

• Ch. 19

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Section 1
Stability in Bonding
3

• Compounds
• Two or more elements combining to make a
  substance
• Compounds have different properties than the
  elements that make them up

4

• Chemical Formula
• composed of symbols and subscripts indicating the
  number of atoms of an element in a compound.
• Subscript
• Means written below

5

• Atoms form compounds when the compound is more
  stable than the separate atoms.
• Noble gases
• Elements in far right column
• Are more chemically stable than other elements
  because they have a complete outer energy level.

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• Stable Compounds
• Elements that do not have full outer energy
  levels are more stable in compounds.
• Atoms can lose, gain, or share electrons to get a
  stable outer energy level.
• Chemical bond
• the force that holds atoms together in a compound.

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Section 2
Types of Bonds
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Forming a bond

• Chemical Bonds
• When two elements come together by either
  transferring or sharing electrons
• When elements lose or gain electrons
• The result of bonding is a net charge of zero

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• Ion
• A charged particle because it has more or fewer
  electrons than protons.
• Cation
• Positively charged ion
• When an atom loses an electron
• Anion
• Negatively charged ion
• When an atom gains an electron

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• Molecules
• Neutral particles formed as a result of sharing
  electrons.
• Covalent bond
• the force of attraction between atoms sharing
  electrons.

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• Ionic bond
• the force of attraction between opposite charges
  of the ions
• Chemical Bonding
• Result is a neutral compound.
• Sum of the charges is zero.

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• Atoms can form double or triple bonds depending
  on whether they share two or three pairs of
  electrons
• Saturated
• all single bonds
• Unsaturated
• Not all single bonds
• Must contain at least one double or triple bond

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• Polar molecule
• Opposite ends have opposite charges
• Nonpolar molecule
• electrons are shared equally.

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• Ionic Compounds
• With ions (cations and anions)
• Between metal and non-metal
• Transfer of electrons
• Covalent Compounds
• With molecules
• Between two non-metals
• Sharing of electrons

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Section 3
Writing Formulas and Naming Compounds
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• Chemists use symbols from the periodic table to
  write formulas for compounds.
• Binary compound
• composed of two elements
• Oxidation number
• how many electrons an atom has gained, lost, or
  shared to become stable
• The apparent charge on an element

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• To write formulas
• Use oxidation numbers
• Least common multiples
• When writing formulas, remember that the compound
  is neutral.
• A formula must have the correct number of
  positive and negative ions so the charges balance
• The formula must have a neutral charge

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Writing Binary Compounds

1. Write down first element its oxidation number
2. Write down second element its oxidation number
3. Add multiples of the appropriate element until
   total charge is zero
4. Use subscripts to show ratio of the atoms of each
   element

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Calcium Oxide

• Ca 2
• O-2
• 2 -2
• So 1 Ca and 1 O
• CaO

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Lithium Nitride

• Li 1
• N-3
• 1 -3
• 1
• 1
• So 3 Li and 1 N
• Li3N

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Magnesium Phosphide

• Mg 2
• P-3
• 2 -3
• 2
• -3
• 2
• So 3 Mg and 2 P
• Mg3P2

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Potassium Sulfide

• K 1
• S-2
• 1 -2
• 1
• So 2 K and 1 S
• K2S

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Naming Binary Compounds

1. Write down name of first element
2. Write down name of second element
3. Change the ending of the second element to ide

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NaCl

• Sodium
• Chlorine
• -ide
• Sodium Chloride

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K2O

• Potassium
• Oxygen
• -ide
• Potassium Oxide

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• Poly
• Means many
• Polyatomic ion
• positively or negatively charged, covalently
  bonded group of atoms
• Many atoms

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• Hydrate
• compound with water chemically attached to it
• Binary covalent compounds
• Name by using prefixes to indicate how many atoms
  of each element are in the compound

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Prefixes forCovalent Compounds

1. Mono-
2. Di-
3. Tri-
4. Tetra-
5. Penta-
6. Hexa-
7. Hepta-
8. Octa-
9. Non-
10. Dec-