Transcript Chemical Bonding Chapter 13 Covalent Bonds Section 3 Covalent Bonds • A chemical bond is formed when two atoms share valence electrons is called a.

Chemical Bonding
Chapter 13
Covalent Bonds
Section 3
Covalent Bonds
• A chemical bond is formed when two atoms share
valence electrons is called a covalent bond.
• Covalent bonds form between two or more
nonmetals.
• In a covalent bond, both atoms attract the two
shared electrons at the same time.
• Ex: two fluorine atoms share a pair of e- so they each have
full valence shells.
Covalent Bonds and Molecules
• molecule – two or more atoms chemically combined in a
specific ratio, smallest piece of a compound
• molecular compounds consist of molecules having covalently
bonded atoms
• Characteristics of Molecular Compounds:
• Much weaker than ionic bonds
• Have much lower melting/boiling points.
• All nonmetals
• Most molecular compounds
are poor conductors of
electricity and are often used
as insulators.
• Ex: plastic and rubber
• Pure water does not
conduct electricity.
Diagramming Covalent Bonds
• Electron-dot diagram – (also
known as a valence dot diagram)
the symbol for the element
surrounded by as many dots as
there are valence electrons
• How to Write Them
• The dots are written in pairs.
• Begin at the right of the element
with single dots, add dots to the
top, left side and bottom. Then
begin adding a second dot to each
side with any remaining valence e-.
Diagramming Covalent Bonds Cont…
• The # of valence e- needed to fill the valence shell is
the # of bonds the element can form.
• Oxygen has 6 valence e-, so it can form 2 bonds.
• Nitrogen has 5 valence e-, so it can form 3 bonds.
• Double bond -- when 2 pairs of e- are shared
between atoms
• Triple bond -- when 3 pairs of e- are shared between
atoms
The Simplest Covalent Molecules
• The simplest molecules are made up of
two bonded atoms. Two atoms of the
same element bonded together are
called diatomic molecules.
• Elements found in nature as diatomic
molecules are known as diatomic
elements.
More Complex
Molecules
• Carbon has 4 valence electrons, leaving
4 empty spaces in its outer shell, so
carbon can form ___ covalent bonds.
Metallic Bonds
• Electrons in the outer energy levels of metals are
not held tightly to the atom. They form a “shared
pool” of electrons.
• Metallic bonds are formed when the positive metal
atoms attract the pooled electrons.
• Movement of Electrons Throughout a Metal
•
The valence shells of the metal atoms overlap, allowing
electrons to flow freely throughout the metal.
Properties of Metals
•
Conducting Electrical Current
• Since electrons are free to move between atoms,
metallic bonding allows metals to conduct electricity
very easily.
•
Reshaping Metals
• Ductility/malleability – since electrons slide easily
throughout metals
•
Bonding Without Breaking
• Moving electrons allow metals to bend and keep the
new shape.
Ionic Bonds
Covalent Bonds
Metals and Nonmetals Nonmetals and
nonmetals
Gain or Lose
Electrons
Share Electrons
High melting points
Low melting Points
Ions conduct
Does not conduct
electricity. Solid ionic electricity; insulators
compounds do not.
Stronger bond and
Weaker bond
stronger charges