Valence Electrons Atoms want to be stable. To be stable, they want 8 valence electrons. Valence electrons are the electrons in the outer energy level. Noble gases are thus the most stable elements, group 18, because they have 8 valence electrons. The more valence electrons an atom has, the more stable it is, and the less it will react with other atoms.

Covalent Bonds Covalent bonds are formed by atoms sharing valence electrons. Triple covalent bonds are the strongest. Covalent compounds are poor conductors with low boiling and melting points.

Ionic Bonds Ionic bonds form to create more stability. They are formed by a bond between positively and negatively charged atoms. An ion is an atom that is no longer electrically neutral because it has gained or lost an electron(s). Negatively charged atoms attract positively charged atoms and vice- versa. Formed between a metal and a nonmetal.

Ionic Bond

Chemical Bonds A force that holds atoms together is a chemical bond. Polar molecules have a slight positive and a slight negative end because the atoms in them do not share electrons equally.

Metallic Bonds This chemical bond is formed when positively charged atoms share their electrons.

Periodic Table The periodic table has 18 columns, called groups. Atoms in the same group have similar properties. The period table also has rows, called periods. The periodic table is arranged by atomic number, increasing from left to right by one for each element. Metals mostly on the left, gases on the far right. This Photo by Unknown Author is licensed under CC BY-NC-SA

Electron Dot Diagrams H2O 2 hydrogen, 1 oxygen Symbol surrounded by dots; one dot for each valence electron. Chemical Formulas H2O 2 hydrogen, 1 oxygen C6H22012 6 Carbon, 22 Hydrogen, 12 Oxygen