Download 2.5 Chemical Bonding - Lighthouse Christian Academy

Chemical Bonding
(Sec 7.2 pg 176 – 181)
• The physical forces that join or connect atoms together are
called chemical bonds.
• Remember: BONDING involves interactions b/w the
ELECTRONS of 2 or more atoms.
• There are 2 general types of bonding (ionic and covalent):
• Oppositely charged ions (metals and non-metals)
have a strong attraction for one another and, as a
result, are held tightly together.
• This is known as ionic bonding and serves to build
atoms into compounds called ionic compounds.
• In ionic bonding, a transfer of valence e occurs.
• Ionic bonding always occurs b/w metals and nonmetals
• Some properties of ionic bonds:
– Form crystals (See Fig.2 p.177)
– Have high melting points (LOTS heat needed to separate
tightly bound ions)
– Hard and brittle
– Conduct electricity when dissolved in water.
• Another type of bonding occurs when non-metals ‘share’
their valence e with other non-metals to complete their
valence shells.
• This bonding is called covalent bonding and builds atoms
into covalent or molecular compounds.
• Therefore, in covalent bonding, a sharing of valence
electrons occurs (always b/w 2 non-metals).
• Some properties of covalent bonds:
– Form crystals
– Do not conduct electricity when dissolved (please see
Fig.9 p.181)
– Have low melting and boiling points.
• Covalent bonding can explain the existence of diatomic
elements (please see Fig.4&5 p.178)
• The third kind of bond is a cross between the ionic bond
and the covalent bond.
• It is called the polar covalent bond and it forms when the
two elements share valence electrons but one element
pulls the electrons closer to its nucleus.
• The diagram on the right shows the breakdown of pure
substances:
• Atoms are the smallest unit of elements (in chemistry…)
• Ions are the smallest unit for ionic compounds.
• Molecules are neutral particles that consist of 2 or more
atoms covalently bonded together (Fig.6 p.178) – they form
molecular compounds
Check your Understanding
Pg 182 #1-5, 7, 10