Chemical Bonding and Review

Electrons & Chemical bonding Chemical bonding is the joining of atoms to form new substances And the force of attraction that holds two atoms together is called a chemical bond

Electron arrangement First energy level closest to the nucleus holds up to 2 electrons Electrons will enter the second energy level only after the first is full. The second level holds up to 8 electrons Once the second energy level is full, the electrons will enter the third energy level which holds up to 8 electrons

Valence Electrons level so it has an electron valence of 7 Definition: electrons in the outermost energy level of an atom Example: Cl (Chlorine) has 7 electrons in its outer most energy level so it has an electron valence of 7

Noble or Inert Gases Unreactive nonmetals Have complete set of electrons in outer energy level – 8 electrons except Helium which has 2 So, they do not lose or gain electrons All are found in Earth’s atmosphere in small amounts – Argon which is most abundant

Lewis Dot Diagram A model that shows only the valence electrons in an atom Helpful when predicting how atoms might bond

Example of Covalent bond using Lewis dot diagram

Ionic Bonds Definition: force of attraction between oppositely charged particles (ions) Positive ions – lose electrons - Groups 1,2, 13, and 14 Negative ions – gain electrons - Groups 14, 15, 16, and 17 Lithium loses an electron to fluorine thus the charge on Li is +1 and F is -1

Ionic compounds Bond in repeating three-dimensional patterns called Crystal lattice The arrange as alternating positive and negative ions forming a solid such as table salt (sodium chloride) Arrangement of bonded ions in a crystal lattice determines the shape of the crystals of an ionic compound

Covalent Bonding Definition: force of attraction between the nuclei (where the protons are – positive charge) of atoms and the electrons shared by the atoms A molecule is a neutral group of atoms held together by covalent bonds

Simpliest Molecules All molecules are composed of at least 2 covalently bonded atoms Diatomic molecules consist of two atoms bonded together There are 7 diatomic molecules: hydrogen, oxygen, nitrogen, fluorine, chlorine, bromine, and iodine

Metallic Bonding Definition: force of attraction between a positively charged metal ion and the electrons in a metal outer valence electrons are shared among all atoms, and are free to travel everywhere.

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Quiz The force of attraction that holds two atoms together is a ________. (crystal lattice or chemical bond) Charged particles that form when atoms transfer electrons are ______. (molecules or ions) The force of attraction between the nuclei of atoms and shared electrons is a(n) _____. (Ionic bond or covalent bond) Electrons free to move throughout a material are associated with a(n) _____. (ionic bond or metallic bond) Shared electrons are associated with a _____.(covalent bond or metallic bond)

Quiz (continued) 6. For each atom below, write the number of electrons it must gain or lose to have 8 valence electrons. Then calculate the charge of the ion that would form. Calcium (Ca) c. bromine (Br) Phosphorus (P) d. sulfur (S)

Answer to quiz 1.Chemical bond 2. Ions 3. Covalent bond 4. Metallic bond 5. Covalent bond 6a. Lose 2 electrons; 2+ b. gain 3 electrons; 3- c. gain 1 electron; 1+ d. gain 2 electrons; 2-