1st Period: Hydrogen and helium—Electrons go into the first energy level. After the first level has two electrons, the next electron goes into the second level. 2nd Period: Lithium to neon—Electrons ...

The periodic table of chemical elements, often called the periodic table, organizes all discovered chemical elements in rows (called periods) and columns (called groups) according to increasing atomic ...

This year we celebrate the 150 th anniversary of Mendeleev’s achievement in formulating the structure of the periodic table that we use today. He announced his structure in 1869, but the challenge of ...

It would help if you've got a periodic table in front of you. TULELA: Go for it. SUNAYANA: Nitrogen. TULELA: The answer is period 2. Group 5. Two shells. Five electrons in the outer shell.