GUIDE深度 · Deep dive
How to Read the Periodic Table
The table is ordered by atomic number: rows are periods and columns are groups. Atomic number equals protons and defines the element; atomic mass is the weighted average of isotopes. Learn the first 20 elements, then expand by group.
Three numbers
Atomic number = protons.
Mass number = protons + neutrons.
Atomic mass is a weighted average, not an integer.
Memory order
Start with H-Ca (1-20).
Then learn groups: alkali metals, halogens, noble gases.
FAQ
Does atomic number change?
No; changing protons makes a different element.
Why is atomic mass fractional?
It is a weighted average of isotope abundances.