Stop 2 of 12 · The path
Atoms — the bits stuff is made of
Every element is one kind of atom. Protons fix which element, electrons fix the charge, neutrons fix the weight.
Bench tool
The atom builder
Slide protons to change the element; unbalance electrons to make an ion.
How it works
- Protons decide the element. 1 is hydrogen, 6 carbon, 8 oxygen. This count is the atomic number Z.
- Electrons decide charge. Equal to protons: neutral. Fewer: positive ion. More: negative ion.
- Neutrons decide the isotope. Same element, different weight. Carbon-12 and carbon-14 behave the same chemically.
Worked examples
Oxygen. 8 protons, 8 electrons: neutral O. Lose 2 electrons → O²⁺.
Sodium becomes Na⁺. 11 protons, 10 electrons: charge +1. That is why salt conducts when melted.
Carbon-14. 6 protons, 8 neutrons. Chemically carbon, heavier — used for dating old wood.
Where it goes wrong
Electrons weigh almost nothing. Ions change charge, barely change mass.
Isotopes are not ions. Isotope = neutrons differ. Ion = electrons differ.
Try it at home: build-a-salt ion check
Paper ions. Draw Na (11p/11e) and Cl (17p/17e) circles, move one electron dot from Na to Cl, and write the new charges. They flip to +1 and −1 — ions are unbalanced electrons, not new elements.
For teachers
Learners mix up ions and isotopes — probe by asking what changes when you add a neutron vs an electron. Quickest check: give 6p/8n/6e and ask for element, mass number, and charge.