Periodic table of Elements

• The number (the roman ones) of main group in the table of elements tell us the amount of outer most electrons (valence electrons) (exc. alkali metals all have one electron in the outer most shell...)
• The period number tells the amount of electron shells in use (horisontal line).
• The amount of protons is the atomic number of an element and the elements are all organised according to their atomic number (amount of protons in their nuclei).
• The amount of neutrons on each element varies.
• The amount of negatively charged electrons is the same as the amount of positively charged protons in a neutral atom.