How to Determine the Charges in Atoms

The periodic table is a crucial tool for determining the charges in an atom.

Atoms gain and lose electrons, but this will not change the atom itself. When electrons move it means the bond is changing. An atom with a missing electron or an atom that has gained an electron is called an ion. Determining the charge of an atom or series of atoms requires several steps, so it's important to check your work to ensure you have the correct information as you go.

Things You'll Need

• Periodic table
• Paper
• Pencil

Instructions

1. Find the atoms on the periodic table and write down the group number for each atom. Groups nine and 10 are considered as group "VIII B." When you're searching for an atom under groups 11 through 18, subtract 10. The difference is the number you need to write down. These numbers signify only the outer electrons in an atom.

2. Add the electrons together if you have two or more of a single atom. For example, if you're finding the charge for NO3 then you'll need to multiply 3 by 6 because oxygen is under the 16 group and NO3 has three oxygens.

3. Create a basic Lewis structure. Oxygen would be an "O" with six dots around the edges. Two dots would be on top of the "O" and two dots would be on each side of the "O." If an element has eight electrons then the final pair will go on the bottom.

4. Start connecting the elements in your molecule. If you're drawing H2O, then place a pair of dots on the top of an "O" and a pair to the right edge of the "O." Because hydrogen only has one electron, place one dot under the "O" and to the "left" of the "O." Put the "H" below and another to the left of the "O." Connect the dot to the left of the "O" to the "H," and connect the "O" at the bottom to the other "H." A single line represents two dots and is referred to as a single bond. A double line represents a double bond.

5. Solve for the formal charge. Add the number of non-bonding electrons to the product of the number of bonding electrons multiplied by one-half. Subtract your answer from the number of valence electrons. A negative 1 implies a negative charge, while a positive 1 implies a positive charge. A zero is neutral.

References

• Mr. Everett's Web Page: Copper
• Jefferson Lab: How many protons, electrons and neutrons are in an atom of krypton, carbon, oxygen, neon, silver, gold, etc...?, Steve Gagnon
• Elmhurst College: Lewis Symbols or Diagrams
• Georgia Southern: Formal Charge

Resources

• Web Elements: The Periodic Table on the Web