Chapter 5
Be able to name compounds from chemical formulas -
- Type 1- 1. The cation is always named first and the anion second. 2. A simple cation (obtained from a single atom) takes its name from the name of the element 3. A simple anion is named by taking the first part of the element name (the root) and adding -ide.
- Type 2- 1. The cation is always named first and the anion second. 2. Because the cation can assume more than one charge, the charge is specified by a Roman numeral in parentheses.
- Type 3: Step 1: Name the first element using the full element name Step 2: Name the second element as though it were an anion Step 3 and 4: Use prefixes to denote numbers of atoms, pre-fix mono never used for naming first element
Be able to give chemical formulas from names of compound
Opposite way from rules above
Formula writing with Polyatomic Ions
1. Identify the symbol of the cation (first part of the name) and the anion
The symbol for Iron is Fe and the symbol for Carbonate which is a polyatomic ion is CO3
2. Identify the valence or charge of each symbol and place it in parenthesis just above the symbol
The valence for Iron (III) is 3+ and the valence for Carbonate is 2-
3. Balance the total positive and negative charge on the cation and anion. You ask yourself do the total positive charge and total negative charge add up to zero. If the answer is no then we ask how many of each ion must we have in order to balance charge. We must have the same number of positive charges as we do of negative charges. Another way of saying that is that they must add up to zero. Since an Iron (III) has a +3 charge and the Carbonate ion has a 2- then it would take two Fe3+ units to balance three CO32- units
4. Once you have determined the number of units of the cation and anion those become the subscripts which are placed right after the respective symbol.
Know the polyatomic list
- Type 1- 1. The cation is always named first and the anion second. 2. A simple cation (obtained from a single atom) takes its name from the name of the element 3. A simple anion is named by taking the first part of the element name (the root) and adding -ide.
- Type 2- 1. The cation is always named first and the anion second. 2. Because the cation can assume more than one charge, the charge is specified by a Roman numeral in parentheses.
- Type 3: Step 1: Name the first element using the full element name Step 2: Name the second element as though it were an anion Step 3 and 4: Use prefixes to denote numbers of atoms, pre-fix mono never used for naming first element
Be able to give chemical formulas from names of compound
Opposite way from rules above
Formula writing with Polyatomic Ions
1. Identify the symbol of the cation (first part of the name) and the anion
The symbol for Iron is Fe and the symbol for Carbonate which is a polyatomic ion is CO3
2. Identify the valence or charge of each symbol and place it in parenthesis just above the symbol
The valence for Iron (III) is 3+ and the valence for Carbonate is 2-
3. Balance the total positive and negative charge on the cation and anion. You ask yourself do the total positive charge and total negative charge add up to zero. If the answer is no then we ask how many of each ion must we have in order to balance charge. We must have the same number of positive charges as we do of negative charges. Another way of saying that is that they must add up to zero. Since an Iron (III) has a +3 charge and the Carbonate ion has a 2- then it would take two Fe3+ units to balance three CO32- units
4. Once you have determined the number of units of the cation and anion those become the subscripts which are placed right after the respective symbol.
Know the polyatomic list
Calculation
So for example what is the formula of Copper (I) Oxide?
What is the formula of Calcium Nitride?
- Identify the symbols of the cation and anion
Copper is Cu and Oxide is O - Identify the charge for each and place above the symbol in parenthesis
For Copper I that would be 1+ and for Oxide that would be 2- - Balance the positive and negative charges
Since each Copper is 1+ and each Oxide is 2- then it will take two Cu+ to balance one oxide with a 2- so that
2(1+) + 1(2-) = 0. The numbers outside the parenthesis become the subscripts in the formula - Write the formula placing the subscripts right after the symbol they go with.
Cu2O
What is the formula of Calcium Nitride?
- Identify the symbols of each part of the name
Calcium symbol is Ca and Nitride symbol is N - Identify the charge for each
Calcium belongs from Group 2 which always has a +2 and Nitride will be a single Nitrogen with a -3 charge - Balance charge
Since Calcium is +2 and Nitride is -3 the only way to balance them is to have three Calcium's and two nitrides - Write the symbol beginning with the symbol that is first in the name and include the subscript after each symbol
Ca3N2
Video
This video tell you how the write out a compound name.
This video tell you how the write out a compound name.