#### RELATIONSHIP OF Elements_Atoms & Compounds_Molecules

Stoichiometric information that is associated with elements, compounds and equations.

The following information relative to an element and compound is absolutely necessary to commit to memory.  It is the basis that will be used to calculate any stoichiometric information relative to an element, compound.

ELEMENTS:   An element is one of the two purest forms of matter.  It is homogeneous (uniform) in composition.  The smallest unit of the element is called the ‘atom’. All atoms of a particular element isotope are identical.  They all have exactly the same number of protons. There are 104 elements listed in the periodic table.  The atom of each element is unique and can be identified by its number of protons.

An atom of a particular element has a specific combination of electrons & protons; however, the number of neutrons may vary slightly for different isotopes of that atom.

1. 1 mol of an element weighs its listed mass in grams
2. 1 mol of an element has 6.022 x 1023 atoms of that element.
3. 1 atom of an element weighs its listed mass in amu  (atomic mass units)
4. 1 amu = 1.66 x 10-24  grams
5. The mass of a compound is equal to its collective mass of all the atoms that it contains.

Example:      CxOyNz

COMPOUND:  A compound is the second purest form of matter.   When two or more elements combine in a specific ratio by mols, it forms a specific compound.  Specific compounds will form in a specified ratio of elements. Any other ratio of these elements will form another compound. The compound is expressed by a formula and the ratio of each element is indicated by the subscript of that element in the formula for that compound.

Example:      CxHyOz

x, y  &  z  represent whole numbers that express the mol ratio of each element in the formula   CxHyOz.

1.  1 mol of a compound has a mass in grams equal to its collective masses of

all the elements that it contains in grams.

2. 1 mol of a compound has 6.022 X 1023 molecules of that compound

3. 1 molecule of a compound has a mass equal to its collective masses of all

the atoms that it contains in amu’s.

EXAMPLE:   1 mol of C2H6O3

The following equivalencies are derived for 1 mol of C2H6O3 and are for 1 mol of C2H6O3  ONLY.  Similar equivalencies may be derived for each individual formula of a compound.   Each individual formula  has its unique equivalencies that may be used as mathematical stoichiometric conversions.

I.

1a.  1 mol of C2H6O3  contains the listed equivalencies in mols  of  each element

below:

(Remember:  a mol of a compound is made up of mols of each element in a

definite ratio, therefore, the subscripts refer to mols of each element. Mol-to-

mol ratios)

1 mol of C2H6O3   has   2 mols of C

1 mol of C2H6O3 has   6 mols of H

1 mol of C2H6O3 has   3 mols of O

Other equivalencies  for C2H6O3  only.  Since each of the expressed mols of the individual elements are all equal to1 mol of the compound.  Each expressed mols of each element is equivalent to each other.

Such as for the compound C2H6O3:  only:

1b.   2 mols of C combine with 6 mols of H

2 mols of C combine with 3 mols of O

6 mols of H combine with 3 mols of O

2a.  1 mol of C2H6O3  contains the listed equivalencies in grams of  each element

below:

2 mols of C   weighs      2   x   12 grams each    = 24 grams

6 mols of H weighs        6    x    1 gram each      =   6 grams

3 mols of O weighs        3    x   16 grams each    = 48 grams

Total mass of a mol of C2H6O3 = 78 grams of C2H6O3

1 mol of C2H6O3 = 78 grams of C2H6O3

Other equivalencies  for C2H6O3  only.  Since each of the expressed grams of the individual elements are all equal to1 mol of the compound.  Each expressed grams of each element is equivalent to each other.

2b.   24 grams of C combine with 6 grams of H

24 grams of C combine with 48 grams of O

6 grams of H combine with 48 grams of O

3.  1 mol of C2H6O  has  6.022 x 1023 molecules of C2H6O3

4.   6.022 x 1023 molecules  of   C2H6O3  = 78 grams of C2H6O3

II. 1 (each) molecule of   C2H6O3   (Remember:  a molecule is made up of atoms,

therefore, the subscripts refer to atoms of each element:  molecule – to – atom      ratios)

1.     1 molecule of C2H6Ohas the listed equivalencies of atoms for each atom

listed below:

1 molecule of   C2H6O3   has    2 atoms of C

1 molecule of   C2H6O3   has    6 atoms of H

1 molecule of   C2H6O3   has    3 atoms of O

2.      1 molecule of C2H6O contains the listed equivalencies of  amu’s for each atom

listed below……

2 atoms of C   weighs      2   x   12 amu each    =   24 amu

6 atoms of H weighs        6    x    1 amu each      =   6 amu

3 atoms of O weighs        3    x   16 amu each     = 48 amu

Total mass of a molecule of C2H6O3     =   78 amu of C2H6O3

3.  1 molecule of C2H6O3     =   78 amu of C2H6O3

You should be able to mentally list similar information that is associated with any formula given.