Periodic Table

History The modern periodic table is based primarily on the work of the Russian chemist Dmitri Voinovich Mendeleev ( ) and the German physicist Julius Lothar Meyer ( ). Working independently, both scientists developed similar periodic tables in Mendeleev receives the credit because he managed to publish his work

The table Mendeleev developed is very similar to the one we use today. He listed elements by similarities and their atomic Weight. It was not until the beginning of the 20 th century, with the knowledge gained about the structure of the atom, that the Correct way of ordering the elements was discovered and the modern periodic table was created

April 1897, Joseph John Thompson (physicist) discovered the electron 1911, Ernest Rutherford (Physicist) discovered the nucleus and in 1920, the Proton. 1932, Ernest Rutherford (physicist) discovered the neutron

Henry Moseley (physicist) discovered every element had a different number of protons in the nucleus and this became known as the atomic number. The unique properties of each of the chemical elements are determined by their number of neutrons, protons, and electrons. Besides determining the properties of a pure chemical element, the neutron, proton, and electron content of its atoms also determines its behavior in relation to other chemical elements

The Modern Periodic Table The Modern statement of the periodic law is that the chemical and physical properties the elements vary in a periodic way with their atomic numbers The periodic table is organized like a big grid. The Elements are placed in specific places because of the way they look and act. The periodic table has rows and columns and they each mean something different

Periods When you look at the picture below, you can see that the rows are different colors. Even though they skip some squares in between, all of the rows go left to right. When you look at a periodic table each of the rows are considered to be different PERIODS.

Periods 

In the periodic table, elements have something in common if they are in the same row. All of the elements in the second row (the second period) have two shells for their electrons. It goes down the periodic table like that.

The Groups The periodic table haw a special name for its columns too. When a column goes from top to bottom, its called a GROUP. The elements in a group have the same number of electrons in the outer shell.

Groups 

So, every element in the first column (group one) has one electron is its outer shell. Every element on the second column (group two) has two electrons in the outer shell.

Hydrogen Hydrogen is special. Hydrogen can have the electrons of two groups, one and seven. To scientists, Hydrogen is sometimes missing an electron. And sometimes it has an extra. Helium is different. It can only have two electrons in its outer shell, but it still gets grouped with elements that have eight.

The elements in between, with the grey color, are called Transition elements. They are not in our main group.