I am the ghost of Dmitri Mendeleev. I created the original Periodic Table of Elements.I have come back from the dead to haunt anyone who fails Ms. Coleman's test, so pay attention!
The Periodic Table of Elements is arranged in order of increasing atomic numbers. It consists of periods and groups.
The rows going left to right on the periodic table are called rows. The period number tells you the number of energy levels or orbitals an element has.
The columns are called groups or families. The group number an element is in tells you the number of valence electrons it contains.
On the Periodic Table of Elements, elements are identified by their atomic number which is how many protons and electrons it has.
2 He Helium 4.003
The number of electrons in the outermost shell of an element determines its reactivity. As you move from left to right down the Periodic Table, reactivity decreases. For example, elements in Group 18 or 8A are the least reactive due to their outermost shell or energy level being full of electrons. These Noble Gases can't gain or lose electrons.
The most reactive groups are 1 and 17. Since Group 1 has only one valence electron, an element in that group only needs to give one away to have an empty ring. Since Group 17 has 7 valence electrons, an element from that group only needs one electron to have a full ring.