Why scientists care
A concrete example
Carbon-12 has 6 protons and 6 neutrons; changing the proton count would create a different element.
Try to notice
Science becomes memorable when a definition is connected to something measurable or observable.
Mendeleev
Periodic table · chemistry · physics
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Core Science · EN
Atomic structure
The key idea
At the scale of an atom, almost all the mass is concentrated in a tiny nucleus. Electrons occupy quantum states around it rather than little planetary tracks. The atomic number counts protons and identifies the element.
Why it matters
Think of the periodic table as a map whose address is the proton count.