Chemical Bonding
Science Investigations
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?
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
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
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
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
Covalent Bonds
Atoms share electrons
Two types:
Polar Covalent: Unequal sharing of electrons
Nonpolar Covalent: Equal sharing of electrons
Covalent Bonds
Rule of thumb:
Two nonmetal atoms that are different = polar covalent
Ex.: CO2, H2O
Two nonmetal atoms that are the same = nonpolar covalent
Ex.: H2
Electronegativity Difference: >0.3-1.7 (polar covalent), 0-0.3 (nonpolar covalent)
Polar vs. Nonpolar
Polar: dissolves in water
Nonpolar: do not dissolve in water
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
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