Unit 4
Compounds and
Chemical Bonding
The Questions
1.
What are chemical bonds?
2.
What are the 2 main types of
chemical bonds?
3.
How do you determine the number
of atoms in a chemical formula?
4.
Why do chemical bonds form?
Valence electrons
 Chemical bonds are formed only between the
electrons in the highest unfilled energy level.
 These electrons are called valence electrons.
Chemical Bonds and Electrons
A chemical bond forms
when atoms transfer or
share valence electrons.
Atoms transfer or share
electrons so they can
become kings (or queens).
In other words, nobel.
This means that each atom
wants to have a completely
full valence level in a
chemical bond.
This makes each atom
happy.
This is everyones goal in
life…
Covalent Bonds
A covalent bond is
formed when atoms
share valence
electrons.
Covalent bonds are
formed between a
nonmetal and
nonmetal.
This is important!!!!
Ionic bonds
 Ionic bonds are bonds in which valence electrons are
transferred from one atom to another.
 When an atom loses or gains an electron it is known as
an ion and the ion has a charge (not neutral).
 Opposites attract so the atom that is positive is attracted
to an atom that is negative.
 Ionic Bonds form between metals and non-metals.
What type of bond?
H2O - Water
Covalent
NaCl – Table salt.
Ionic
CO2 – Carbon Dioxide
 Covalent
Chemical Formulas
A compound’s chemical formula tells
you the ratio of atoms of each element
in the compound.
Chemical Formulas
How many Carbons, Hydrogens are there
in:
C8H18
How many Carbons, Hydrogens and
Oxygens are in:
C6H12O6
How many Na, C, H and O are in the
following:
Na2(HCO3)2
Why chemical bonds form
It takes energy to
separate atoms that are
bonded together.
The same energy is
released when chemical
bonds form.
Atoms form bonds to
reach a lower energy
state.
Reactivity
In chemistry, reactive means an element
readily forms chemical bonds, often
releasing energy.
Some elements are more reactive than
others.
The closer an element is to having a full
valence energy level (the same number of
valence electrons as a noble gas), the
more reactive the element is.
You may want to label your MAP….
The Answer
1. What are chemical bonds?
A bond that forms when atoms
transfer or share electrons.
2. What are the 2 main types of
chemical bonds?
Covalent and Ionic.
The Answer
3. How do you determine the
number of atoms in a chemical
formula?
By using the subscripts and
Coefficients just like in math.
4. Why do chemical bonds form?
To reach a lower energy state.