Chemical Compounds

Subscript

The smaller numbers or letters beside the element symbol that tell you the number of atoms in the chemical formula, or the state of matter (at room temperature)

Four states of a Compound

(g) - gas, (L) - liquid, (s) - solid, (aq) - aqueous (a solution in which the solvent is water)

Metals

Elements that exist as single compounds

* lose electrons and form positive ions
* are named by their metal name followed by the word “ion” eg) sodium ion, lithium ion

Non-Metals

Elements that can exist as atoms or molecules

* gain electrons and form negative ions


* are named by changing the ending of the non-metal to “ide” then followed by the word “ion” eg) oxide ion, chloride ion

Compounds

Molecules made up of two or more different elements bonded together

Chemical Formulas

The elements in a compound (the symbols) and the amount of atoms belonging to each element (which is shown in the subscript)

Ion

An atom or group of atoms that have become electrically charged

Ionic Compounds

Pure substances formed as a result of the attraction between positive and negative ions

Ionic Compounds Characteristics

Solid at room temp, defined crystal structure, conducts electricity when liquid or dissolved in water, high melting points

How ions are formed

When atoms either lose or gain of electrons

Ion charge

The ion charge of an element on the periodic table (can be found in the superscript). Some elements may have more than one charge

Ionic bonds

formed when a positive and negative ion(s) (charges) attract each other

Steps to name ionic bonds

1. Look at the formula and write the name of the metal ion down first.
2. Write the name of the non-metal ion next but remember to change the ending to “ide”.


3. If the negative ion is a polyatomic ion, just write the name down as you see it on the periodic table.


4. Sometimes you will have a metal ion that has more than one
possible charge. In the name, you must write Roman Numerals (I,
II, III, IV, V, VI, etc) to show which ion it is.

Polyatomic ion

Bonded set of two or more atoms considered to behave as a single unit

Writing formulas (ion)

1. Write down the (+) metal ion first with it’s charge.
2. Write down the (-) non-metal ion second with it’s charge.
3. Keep adding either metal ions or non-metal ions until the positive and negative charges balance…they must add up to zero
4. Count the number of ions of each element. Put the number as a subscript to the right of the ion symbol and remove the ion charge. Note: the number “1” is invisible

Molecular Compound

A compound formed when two or more non-metals join together. They are joint when electrons are shared (a covalent bond)

Molecular compound characteristics

* can be solids, liquids or gases at room temperature
* do NOT conduct electricity when liquid or dissolved in water
* have low melting points

Naming Molecular Compounds

1. Look at the formula and write down the element name for the first atom.

eg) OCl 2 the first element is “oxygen”


2. If there is more than one atom of the first element, add the appropriate prefix.

eg) OCl 2 there is only one oxygen so you leave it as “oxygen”


3. Write the name of the second atom with “ide” ending. Include the prefix. (\*\*\*second element always has a prefix)

eg) OCl 2 the second element is “chloride” and there is 2 of them so you write “dichloride” the name of OCl 2 is “oxygen dichloride”

1 atoms

mono-

2 atoms

di-

3 atoms

tri-

4 atoms

tetra-

5 atoms

penta

6 atoms

hexa

7 atoms

hepta

8 atoms

octa-

9 atoms

nona-

10 atoms

deca-

Writing formulas (molecular)

1. Turn the element names into symbols.
eg) dinitrogen tetraoxide NO
2. Turn the prefixes into subscripts.
3. eg) ==di==nitrogen ==tetra==oxide N2O4

Element

A basic substance that cannot be simplified. All elements are found on the periodic table

Atom

The smallest amount of an element

Molecule

Something formed when 2 or more atoms join together chemically