Atomic Number and Atomic Mass: Get here the easy notes on atomic number and atomic mass for all the first 30 elements. Know how to calculate atomic mass using atomic number.

A "leap second" will be added on June 30 at midnight Coordinated Universal Time (or 8 p.m. EDT). Leap seconds are added occasionally to help keep the atomic clock synced up with the earth's rotation.

Students will begin to look closely at the periodic table. They will be introduced to the basic information given for the elements in most periodic tables: the name, symbol, atomic number, and atomic ...

In the modern periodic table, elements are in order of atomic number in periods and groups. Electronic structures model how electrons are arranged in atoms. Groups in the periodic table - AQA.