Transcript COVALENT BONDS - Toll Middle School

COVALENT BONDS
Chapter 5 Section 3
• Covalent bonds are usually formed
between atoms of nonmetals.
• The force that holds atoms together in a
covalent bond is the attraction of each
atom’s nucleus for the shared pair of
electrons.
• A molecule is a neutral group of atoms
joined by covalent bonds.
• If the atom shares one pair of electrons
they make a single bond.
• If the atom shares two pairs of electrons
they make a double bonds.
• If the atom shares three pairs of electrons
they make a triple bonds.
• Molecular Compound- is a compound
composed of molecules, that are
covalently bonded.
• Compared to ionic compounds, molecular
compounds generally have lower melting
points and boiling points. And, unlike ionic
compounds, molecular compounds do not
conduct electric current when melted or
dissolved in water.
• Unequal sharing of electrons- atoms of some
elements pull more strongly than do atoms of
other elements.
• Unequal sharing of electrons causes the bonded
atoms to have slight electric charges.
• Polar bond is a covalent bond in which
electrons are shared unequally.
• Nonpolar bond is a covalent bond in which
electrons are shared equally.
Questions
• 1. What is an ion?
• 2. Contrast sodium and chloride ions, including
how they form. Write the symbol for each ion.
• 3. What holds the ions together in sodium
chloride? Indicate the specific charges that are
involved.
• 4. Write the formula for calcium chloride
• 5. List three properties of ionic compounds.
• 1. An ion is an atom or group of atoms that
has an electric charge.
• 2. A sodium ion (Na+) forms when a
sodium atom loses one electron and
becomes positively charged. A chloride
ion (Cl-) forms when a chloride atom gains
one electron and becomes negatively
charged.
• 3. Attraction between positive and
negative ions; a sodium ion has a charge
of 1+, and a chloride ion has a charge of
1-.
• 4. CaCl2
• 5.Ionic compounds are hard, brittle
crystals that have high melting points and
can conduct electric current when melted
or in solutions.