Periodic Table
An element's atomic number tells you how many of these particles are in its nucleus.
What are protons?
The symbol H stands for this element.
What is Hydrogen?
The modern periodic table arranges elements in increasing order of this number.
What is atomic number?
This scientist made an early periodic table and left blank spaces for undiscovered elements.
Who is Dmitri Mendeleev?
Unlike mass number, the atomic mass shown in an element box is this kind of value, based on the element's naturally occurring isotopes and their abundance.
What is a weighted average?