The Standard Model is a kind of periodic table of the elements for particle physics ... Physicist J.J. Thomson discovered the electron in 1897, and scientists at the Large Hadron Collider found the ...

Atoms of group 1 elements have one electron in their outer shell ... See the study guide on groups in the periodic table for more information.

The picture shows a close-up of one carbon atom. A hydrogen atom has one proton as the nucleus and one electron in the region outside the nucleus. The electron and proton are attracted to each other.

As you move down a group in the periodic table, the covalent radius increases. Atoms increase in size. This is because of the screening effect of the filled inner electron levels. These electrons ...