atomic structure

• Neutrons have no charge and are found in the nucleus of an atom.
• Protons have a positive charge (+1) and are located in the nucleus.
• The number of protons determines the identity of an element (atomic number).
• Electrons have a negative charge (-1) and orbit around the nucleus at different distances from it, forming shells or energy levels.
• the atomic number of an atom is the number of protons in the nucleus of an atom
• the period tells us how many electron shells there is in an atom
• mendeleev put the elements in order of increasing atomic mass
• Mendeleev left gaps to allow other elements to be discovered later on
• modern periodic table has groups that contain similar properties
• the group of the periodic table tells us the number of electrons in the outer shell of the atom