Formulas and Their Make-up

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Formulas and Their Make-up

• Todays Objectives
• determine what constitutes a formula

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Chemical Formulas

• 1. Tells which elements are present
• 2. The ratio of atoms to one another
• 3. That all the atoms represented are bonded
  together in some way

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Terminology

• Empirical Formulas
• chemical formula that gives the simplest
  whole-numbered ratio of atoms of elements in a
  compound

• Molecular Formula
• chemical formula that indicates the numbers of
  each atom in a compound

• Structural Formula
• formula that indicates how the atoms in a
  compound are bonded to each other

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FREE, FREE, SET THEM FREE!

• Ionic compound
• transfer of electrons from the atom of one
  element to those of another
• involve metals and nonmetals in this bonding
  arrangement
• composed of IONS (atoms searching for
  stability octet rule)

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Ions How do they form?

• Atoms have equal protons and electrons
• Atoms have no net electrical charge
• In certain types of bonding, the atom will lose
  or gain an electron(s)

Magnesium
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Magnesium

• When an atom loses or gains electrons, it is
  called an ion
• Atoms that lose electrons have a positive charge
• Atoms that gain electrons have a negative charge

BOINK!
BOINK!
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CHLORINE

• For the most part, the metals will lose electrons
  and the nonmetals will accept the electrons
• The atoms gain or lose electrons to reach outer
  shell (valence) stability

Electron from magnesium
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ISN'T IT IONIC? DON'T YA THINK?

• Terminology
• A. Monatomic ion
• a positively or negatively charged ion formed
  from a single atom
• indicated by the symbol of the element and the
  charge
• shown on the upper right of the symbol
• Na or Na1 and 02-

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• B. Cation
• positively charged ion
• predominantly metals
• meow baby!
• C. Anion
• negatively charged ion
• predominantly nonmetals
• where is the picnic?

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How to find charges of ions

• Charge sheets
• just look at them
• Periodic table (main group elements only)
• what column is the element in
• remember electron configurations?

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Binary ionic compounds
compound composed of only two elements
Formula writing Rule 1 Cation is always
written first
Rule 2 Determine the charge on each of the
ions
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Rule 3 Select subscripts that will make the
total positive charge equal to the total negative
charge
The compound is to be neutral (same amount of
positive charge as negative charge)
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Ternary Ionic Compounds

• compound composed of more than two elements
• contain a polyatomic ion

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Rule 4 (involving special type of ion)

• Polyatomic ion
• a positively or negatively charged ion
  composed of more than one type of atom
• ex. PO4 3 - , OH1 - , NH4 1
• When using subscripts with polyatomic ions,
  the elements of the ion are put into parenthesis
• Al3 SO4 2- gt (SO4 2-)
• and the subscript is placed outside the
  parenthesis to the right
• (do not keep the charge with the ion)
• Al 3 SO4 2- gt Al2(SO4) 3

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• Least Common Multiple of ionic charge
• ex. Fe 3 CO3 2-
• LCM is 6
• Fe 3 ? goes in to six 2 xs
• CO3 2- ? goes in to six 3 xs
• So then the neutral compound of these two ions
  is
• Fe2(CO3)3

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Naming the CATION

• Monatomic cation
• Use the elemental name of the cation
• Ex.
• Polyatomic cation
• Memorize the name
• Ex.

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Variable charged cation(cation with more than
one charge) 2 methods of naming

• Traditional system
• Uses the Latin root of the element name
• Lower charge ous ending
• Higher charge ic ending
• Must use the ANION to determine the charge of the
  cation
• Ex.

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• Stock system
• Keep the elemental name of the cation
• Roman numerals represent the charge of the cation
• Ex.

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Naming the ANION

• Monatomic anions
• named by using the element name and changing the
  ending to ide
• Ex. Fluorine (atom) ? Fluoride (ion)
• BEWARE ? Exceptions like OH1- (hydroxide), CN1-
  (Cyanide)

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Naming Oxyanions Polyatomic anions with oxygen
in them

• Oxyanions consist of an atom of an element plus
  some number of
• atoms of oxygen covalently bonded to it. The
  name of the anion given
• by the name of the element with its ending
  changed to either ate or
• ite. In some cases, it is also necessary to add
  the prefix per or
• hypo to name the anion.
• From the 7 base "ate" ending oxyanions
• 1. ite suffix means "one fewer oxygen atom
• 2. hypo prefix means "still one fewer oxygen
  atom"
• 3. per prefix means "one more oxygen atom"

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Oxyanions
Name Ion Name Ion Name Ion Name Ion
perchlorate ClO4 1- Chlorate ClO3 1- chlorite ClO2 1- hypochlorite ClO 1-
Bromate BrO3 1-
Iodate IO3 1-
Nitrate NO3 1-
Carbonate CO3 2-
Sulfate SO4 2-
Phosphate PO4 3-
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74 rule
The elements in the 7 will have 3 oxygens
attached to them when ending in -ate Ex. CO3 2-
Carbonate The elements in the 4 will have
4 oxygens attached to them when ending in
-ate Ex. SO4 2- Sulfate
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