1. Chemical Bonding Science Investigations

2. What is a chemical bond? Electrical attraction between the nucleus of one atom and the valence electrons of another An element’s properties are due to its valence electrons What diagram shows the valence electrons of an atom?

3. Octet Rule Atoms will gain/lose electrons through bonding to have 8 valence electrons to be stable like a noble gas Exceptions: Helium and Hydrogen only need two valence electrons

4. Electronegativity Definition: the attraction of an atom for electrons Highest for nonmetals Most electronegative atom is F (Fluorine) and has a value of 4.0 Noble gases do not have a value because they are stable and don’t need electrons

5. Electronegativity Scale (write on periodic table), tells you the type of bond between atoms 0-0.3 = non-polar covalent >0.3-1.7 = polar covalent >1.7- 4.0 = ionic

6. Ionic Bonds A metal atom (positive charge) gives electrons to a nonmetal atom (negative charge) Electronegativity difference: >1.7-4.0 Rule of thumb: A metal (alkali or alkaline earth) + nonmetal = ionic A transition metal + nonmetal = ionic or covalent Examples: LiF, CaO

7. Covalent Bonds Atoms share electrons Two types: Polar Covalent: Unequal sharing of electrons Nonpolar Covalent: Equal sharing of electrons

8. Covalent Bonds Rule of thumb: Two nonmetal atoms that are different = polar covalent Ex.: CO 2, H 2 O Two nonmetal atoms that are the same = nonpolar covalent Ex.: H 2 Electronegativity Difference: >0.3-1.7 (polar covalent), 0-0.3 (nonpolar covalent)

9. Polar vs. Nonpolar Polar: dissolves in water Nonpolar: do not dissolve in water

10. Metallic Bonds Bond between 2 metal atoms Electrons are shared equally between all metal atoms and are free to move from atom to atom (sea of electrons) This makes metals good conductors of heat and electricity