9/28/09
Post date: Sep 27, 2009 6:7:27 PM
Bell Activity: Why do do people have different names?
Just like elements, we give names to compounds to separate them from other compounds
Naming ionic compounds
Ionic compounds are formed because of attractions between positive and negative ions.
Positive ions
are positive because they gave up electrons (lost negative charges)
are called cations
Are usually formed by elements on the left side of the periodic table
Negative ions
are negative because the gained electrons (gained negative charges)
are called anions
Are usually formed by elements on the right side of the periodic table
Naming cations
use the name of the element, plus the word ion
ion charges are determined by number of valence electrons
cations will have + charge, with the charge number being the same as the number of valence electrons
Example: Sodium, Na
When sodium gives up electrons, it becomes an ion called sodium ion
Sodium is in the first column of the periodic table, so it has 1 valence electron
The charge of a Sodium Ion is 1+, so the symbol for this is Na 1+
Example: Barium, Ba
When barium gives up electrons, it becomes an ion called barium ion
Barium is in the second column of the periodic table, so it has 2 valence electrons
The charge of a Barium Ion is 2+, so the symbol for this is Ba 2+
Some elements (transition metals) form more than one type of cation
With these elements, we must include some way to show which ion we're talking about
We do this with roman numerals to show the charge of the ion
Example: Iron, Fe
Iron can give up either 2 or 3 electrons, so it will have either a 2+ or 3+ charge
The Iron ion with a 2+ charge is written as Iron (II) ion
The Iron ion with a 3+ charge is written as Iron (III) ion
Below are the possible charges of the transition metals
Naming Anions
use the name of the element, but change the ending to -ide, plus the word ion
ion charges are determined by valence electron numbers
cations will have - charges, with the number determined by how many electrons they can take
Example: Chlorine, Cl
When chlorine receives an electron, it becomes Chloride ion
Chlorine is in the 7th column (has 7 valence electrons). This means the chlorine takes one more electron, or one negative charge.
The charge for this ion, then, is 1-
The symbol for the Chloride Ion is Cl 1-
Example: Nitrogen, N
When Nitrogen receives an electron, it becomes Nitride ion
Nitrogen is in the 5th column (has 5 valence electrons). This means the Nitrogen takes 3 more electron, or 3 negative charges.
The charge for this ion, then, is 3-
The symbol for the nitride ion is N 3-
Writing formulas for ionic compounds
Start with a cation and an anion
Write the symbols (with charges) for each ion
Put them next to each other, with the cation first
Cross the charges and bring them down to subscript to show how many of each ion is involved
Example: Hydrogen Chloride
Example: Iron (III) oxide
Naming ionics assignment
Write the name and symbol of the ions formed by the following elements:
1. Lithium
2. Beryllium
3. Bromine
4. Sulfur
5. Calcium
6. Cesium
7. Potassium
8. Phosphorus
9. Astatine
10. Oxygen
Example: For Sodium, the name of the ion is Sodium Ion and the symbol is Na 1+
Given the following element symbols, write the name of the compound that each pair forms:
1. Na and Cl
2. H and F
3. Copper (II) and O
4. K and Br
5. Mg and P
Given the following compound names, write the formula of each ionic compound
Sodium chloride
Hydrogen fluoride
Copper (II) oxide
Potassium bromide
Magnesium phosphide