In STEM, we learned about the periodic table. Dmitri Mendeleev created the periodic table in 1869s. Why did he create it? Mendeleev was a chemist teacher. He was writing a chemistry textbook and he needs a way to organize the elements and it would be easier for the student to learn. Here are some facts about the periodic table:
- Mendeleev used atomic mass instead of the atomic number because protons had not yet been discovered when he made his table
- The symbol consists of one or two letters that come from the chemical name
- The first letter is always written in UpperCase.
- The second letter is always written in LowerCase.
- The classes of elements are metals, metalloids, and nonmetals
- Blue stands for metals, orange for metalloids, and green for nonmetals
- Rows of the modern table are called period.
- From left to right across a period, each element has one more proton than the element before it
- The modern periodic table has 7 periods and 18 groups.