Compounds and Formulas

  1. An atom can become stable by gaining, losing or sharing electrons so that its outer energy level is full.
  2. An atom that is no longer neutral because it has lost or gained an electron is called an ion.
  3. A hydrate is a compound that has water chemically attached to its ions.
  4. Valence electrons are the outermost electrons of an atom, which are important in determining how the atom reacts chemically with other atoms.
  5. Ionic bonds form when a metal atom loses one or more electrons and a nonmetal atom gains one or more electrons.  Ionic bonds form between a metal and a nonmetal. 

  1. A compound is a pure substance containing two or more elements that are chemically bonded. (H2O, CO2, CH4)
  2. Covalent bonds are created when two or more nonmetal atoms share electrons. Atoms of many elements become more stable by sharing electrons.

           

  1. The neutral particle formed when atoms share electrons is called a molecule. (H2, O2, N2)
  2. A chemical formula indicates the kind and number of atoms in a compound.
  3. A subscript is a number that tells how many atoms of an element are in a unit of the compound. Ex.: H2O
  4. A superscript is a positive or negative symbol and a number written above to represent the oxidation number of the element.  Ex.: Ba+2 ,  Cl-  

Familiar Name

Chemical Name

Formula

Lye

Sodium hydroxide

NaOH

Milk of Magnesia

Magnesium hydroxide

Mg(OH)2

Ammonia

Ammonia

NH3

Stomach acid or gastric juice

Hydrochloric acid

HCl

Type of sugar (body/carbohydrates)

Glucose

C6H12O6

Marsh gas

Methane

CH4

Carbonic acid gas

Carbon Dioxide

CO2

 

Nitrogen gas

N2

 

Oxygen gas

O2

Table Salt

Sodium chloride

NaCl

Water

 

H2O

 

Valence Electrons

***Helium (He) has only 2 valence electrons

***transition elements have varying valence electrons

 

  1. Reactants are the substances that exist before the reaction begins.
  2. The substances that form as a result of the reaction are called the products.
  3. A chemical equation is a shorthand method of writing what happens in a chemical reaction. Chemical equations use symbols to represent the reactants and products of a reaction, and sometimes show whether energy is produced or absorbed. 

Ex: 2H2 + O2  →   2H2O +  energy

  1. All organisms require energy for their chemical reactions. Photosynthetic organisms such as plants use light energy to produce a carbohydrate (glucose). Glucose can be used at a later time to supply the energy needs of the cell. Photosynthesis is therefore a process in which the energy in sunlight is stored in the bonds of glucose for later use. 

Equation for Photosynthesis:

6CO2 + 6H2O + Energy ® C6H12O6 + 6O2

 

  1. The reactions within cells which result in the synthesis of ATP using energy stored in glucose are referred to as cellular respiration.

Equation for Cellular Respiration:

C6H12O6 + 6O2 ® 6CO2 + 6H2O + Energy

 

  17. Be able to count the # of elements and the # of atoms in a chemical equation:

        Example----   2H2 + O2 arrow2H2O

        Reactants—4 hydrogen and 2 oxygen; Products—4 hydrogen and 2 oxygen

        Two elements are in the equation: hydrogen and oxygen