Body chemistry / QUICK SHORT
Two Extra Electrons Don't Make a New Element
Use an oxygen atom to distinguish element identity from electric charge.
Read the companion guide & try the questions ↓GO BEYOND THE VIDEO
Learning companion
Use three separate counts to solve this puzzle: protons identify the element, electrons help determine charge, and neutrons distinguish isotopes of that element.
Original study notes by Anatomy in Minutes · Updated October 14, 2026
Keep identity separate from charge
An oxygen atom has eight protons. A neutral oxygen atom also has eight electrons, so its positive and negative charges balance. If a particle with those same eight protons has ten electrons, its net charge is minus two. It is still oxygen because its proton number has not changed.
The symbol O²⁻ describes a single oxygen ion with a charge of minus two. It is different from O₂, a molecule containing two oxygen atoms. A small raised charge and a small lowered atom count communicate different information; reading them as interchangeable changes the chemistry.
Change one count at a time
Adding or removing neutrons changes the isotope and the mass, but not the atomic number. Changing the number of protons changes the element itself. Ordinary chemical reactions rearrange electrons and bonds; they do not normally change one element into another.
For a paper model, make three columns labelled protons, neutrons and electrons. Start with 8, 8 and 8. Change only the electron count to 10 and explain the charge. Then restore eight electrons and change only the neutron count to 10. This second comparison creates a different oxygen isotope, not the same change as making an ion.
Key concepts
- Atomic number
- The number of protons in a nucleus.
- Ion
- A particle with a net electrical charge because positive and negative charges do not balance.
- Isotope
- One form of an element distinguished by its neutron number.
Check your understanding
Take 3–5 minutes independently. Write an explanation in your own words or sketch a labelled model on paper before opening each answer. These are original practice prompts; nothing is submitted or graded.
A particle has 8 protons and 7 electrons. What is its element and net charge?
Show reasoning
It is oxygen with a +1 charge: eight positive charges and seven negative charges leave one net positive charge.
Why does O₂ not mean the same thing as O²⁻?
Show reasoning
The subscript counts two oxygen atoms in a molecule. The superscript gives the net negative charge on a single oxide ion.
Sources and further reading
Use these references to check the science and explore the topic in more detail. The notes above are an original learning companion, not a transcript or copied textbook passage.
Illustrations and AI-assisted scenes simplify scale, timing and anatomy. They are educational representations, not clinical recordings or evidence about an individual. This page provides general education, not diagnosis or treatment.
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