March 21st Chemical Compounds and Formulas and Diagrams 21

Chemical Compounds and Formulas

Chemical Compounds are pure substances that contain two or more different elements in a fixed proportion. They are formed when elements combine together in chemical reactions.   For example: Water (H2O) – there are always twice as many hydrogen particles as there are of oxygen particles.

A chemical formula is the combination of symbols that represents a particular compound. A chemical formula indicates which elements are found in the compound, as well as the number of atoms of each element that are found in the compound.

Examples: NaCl – 1 atom of Na – sodium - 1 atom of Cl – chlorine H2O – 2 atoms of H – hydrogen - 1 atom of O - oxygen

Rules For Writing The Formulas for Ionic Compounds

Examples: Sodium chloride Magnesium Oxide NaCl - Na (metal) – sodium - Cl (non-metal) – chloride Mg2O3 -Mg (metal) – magnesium - O (non-metal) - oxide Sodium chloride Magnesium Oxide

Try These Ca3P2 – Li3N – K2S –

Try These Ca3P2 – Calcium phosphide Li3N – Lithium nitride K2S – Potassium sulfide

Write the chemical name for the following ionic compounds.   CoSe HgF2 Na3P Ba3As2 CaBr2

Ball and Hook Diagrams The number of atoms varies from compound to compound. The number of atoms in a compound is determined by the combining capacity of the elements involved. Hook Diagrams show the bonding capacity and number of bonds. All bonds (hooks) must be filled.

The result is the compound calcium chloride (CaCl2) All hooks must be filled to satisfy both substances. Unsatisfied The result is the compound calcium chloride (CaCl2)