Writing Chemical Formulas

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Writing Chemical Formulas
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Metals vs Nonmetals
Metals Nonmetals
Lose electrons (e-) Form Cations ( ions) Gain electrons (e-) Form Anions ( - ions)
Attracted to Cathode Attracted to Anode
Positive Ions Protons gt Electron
Cation Negative Ions Protons lt Electron
Anion
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OXIDATION NUMBER

• is the overall charge on an ion after it has lost
  electrons (metals) or gained electrons
  (non-metals).
• When ions are combined together to form
  compounds, THE OVERALL CHARGE OF THE COMPOUND
  WHICH RESULTS MUST BE ZERO OR NEUTRAL.

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Subscripts

• Subscript Small numbers placed to the lower
  right of the symbols.
• In chemistry this indicates the number of atoms
  of an element.
• When there is only 1 atom of an element the
  subscript is not written.
• Example SiO3
• one silicon atom
• three oxygen atoms

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Parenthesis

• When there is a parenthesis in a chemical formula
  the chemicals inside are multiplied by the number
  outside.
• Example
• Ca(OH2)2
• 1-- Calcium atom.
• 2 -- Oxygen atoms.
• 4 -- Hydrogen atoms.

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Coefficients

• Coefficient A large number placed in front of a
  chemical formula. This number indicates how many
  of each molecules there are.
• Everything in the formula is multiplied by the
  number in front.
• 3MgCO3
• 3 atoms of Mg
• 3 of C
• 9 of O

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Writing Chemical Formulas

• To write chemical formulas you need to know
• Which elements are involved
• The number of electrons (e-) that elements lose,
  gain, or share to become stable

NOTICE METAL ION IS ALWAYS WRITTEN FIRST
NON-METAL ION IS WRITTEN LAST
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SWAP DROP Method

• When ions are combined to form compounds, THE
  OVERALL CHARGE OF THE COMPOUND WHICH RESULTS MUST
  BE ZERO OR NEUTRAL.
• 1. If a the oxidation s cancel do not swap
  drop
• Lithium and Fluorine
• Li Fl- LiFl
• 2. If the oxidations s do not cancel, swap
  drop
• Aluminum and Oxygen
• Al3 O2- Al2O3

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Write a correct formula for the compound, which
would form between.

• calcium and sulfur
• cesium and oxygen
• aluminum and oxygen
• sodium and sulfur
• potassium an oxygen