All matter is made up of atoms . Elements are substances consisting of only one kind of atom , and they cannot be broken down into simpler matter . The particles that make up the elements are atoms or molecules . These particles may be arranged in several ways . The atom consists of a tiny nucleus made up of protons and neutrons . Electrons suround the nucleus . In a neutral atom , the number of electrons is identical to the number of protons . In an ion ( an electrically charged atom ) , the number of electrons does not equal the number of protons . The elements are organized in the periodic table according to their atomic number . Elements that are in the same column in the periodic table have similar properties and are referred to as a “ chemical group . ” Concepts : Atom Element Nucleus , Electron “ cloud ” Electron , Proton , Neutron Electrical ( electrostatic ) forces Atomic number Molecule Lattice Ion Periodic table Chemical group
אל הספר