The Elements and Mendeleev

   

      Elements are the differents combinations of atoms. There are 112 elements, 92 of which are natural elements. Some atoms will bond with other atoms, while others will not bond. If an atom has a full valence electron shell (refer to "Valence Electrons"), then it will not bond with any other atoms. For example, sodium (Na) has 1 valence electron and chlorine (Cl) has 7 valence electrons. Since sodium has only 1 valence electron, it will want to get rid of it, rather than try and gain 7 more. Chlorine has 7 valence electrons, so it will want to gain 1 valence electron, rather that try and lose all 7. That means if the sodium atom gives up its 1 electron to the chlorine atom, then the chlorine atom will have a full outer shell. Now the chlorine atom has a full outer shell and will not bond with any other atoms. Oxygen, carbon, hydrogen and nitrogen make up 96% of the human body weight. The Periodic Table is organized from lowest atomic number (1) to highest atomic number (118). A man named Dmitri Mendeleev was the first to organize all of the known elements into groups and families. Groups/families are the columns in the Periodic Table (up and down/vertical). Periods are the rows in the Periodic Table (side to side/horizontal).