CHEMICAL BONDING
A little background
info first…
Elements

Substance that cannot be separated
or broken down into simpler
substances by chemical means.
Ex’s- any box on the periodic table

Made of only 1 type of

atom
The smallest unit of an element that
maintains the properties of that element


HUH?
The smallest unit of an element that
maintains the properties of that element???

The element sodium has certain properties
 11
protons, 11 electrons, etc and that determines
properties like boiiling point, etc.
Compounds
Molecules made by
atoms of two or more
elements bonded
together -always in a
definite ratio
NaCl (sodium
chloride/salt)

Elements

Molecules made of
just one element
Na (sodium)
Molecules

Two or more atoms bonded together…
 They
can be two of the same element or two
different elements (compounds)
 All compounds are molecules, but not all molecules
are compounds.
 Ex- O2, NaCl, etc.
Compounds cont…

Substance made of atoms of 2 or more different
elements that are CHEMICALLY combined.


Means they are bonded by the electrons!
Elements are combined in a definite way and this
changes their properties
Na- lethal if ingested
Cl- lethal if ingested
NaCl- table salt
Let’s start the real notes…
Compound/Molecule



Chemical combination of 2 or more
atoms/elements.
Properties of the compound are unlike those of the
elements that make it. (table salt ex)
Represented by a formula that gives the ratio of
atoms of the elements.
 Ex-
The formula NaCl tells you that salt is a compound
made of one Na and one Cl.
 The
ratio is then 1:1
Chemical Bond
Force which holds atoms together.
 3 Types:

Metallic
 Ionic
 Covalent

Polar
 Nonpolar

Metallic Bonds




Formed between 2 or more metal atoms (elements).
Valence electrons overlap.
The electrons are free to move about all the atoms;
therefore, they are good conductors of electricity.
Ex) Mg, Cu, Fe, etc. form these types of bonds
Ionic Bonds (formed in ionic compounds)

IONS are the basic unit (atom with a charge).
How are these ions made?



Reminder…
What charge does an electron
have?
So what would happen to the
atom if they LOSE one? Would
they get more positive or more
negative overall???
ION PREDICTION FROM
PERIODIC TABLE…
IONS


If you mess with the electrons you change the
overall charge of the atom…an atom that is no
longer neutral is called an ION.
ANION- has a negative charge
 Means

you added an electron!
CATION- has a positive charge
 Means
you lost an electron
Let’s look at our families- What ion will
each form?

It all starts with the noble gases…
Everyone wants to be NOBLE
These are the “magic numbers”


Each of these atomic numbers will make a “full outer
shell”
Other families will lose or gain electrons to get the
these “numbers”
Alkali Metals

All (except hydrogen- of course) will lose one
electron to form a __________ charge.

(+1)
Alkaline Earth Metals

All will lose two electrons to form a __________
charge.

(+2)
ExA neutral Mg atom has 12 protons and 12 electrons
(+12) + (-12) = 0
A Mg ion has 12 protons and only 10 electrons
(+12) + (-10) = +2
Boron Family

All will lose three electron to form a ____ charge.

(+3)
We don’t do much with the Nitrogen
and Carbon families in ion
formation…you will understand more
about why soon…
Oxygen Family

All will gain two electrons to form a __________
charge.

(-2)
ExA neutral Oxygen atom has 8 protons and 8 electrons
(+8) + (-8) = 0
An Oxygen ion has 8 protons and 10 electrons
(+8) + (-10) = (-2)
HALOGENS

All will gain one electrons to form a __________
charge.

(-1)
How about those noble gases?

They will NOT FORM IONS!!!
How do ions stick together?

Force of attraction between
oppositely charged ions.





(anion & cation)
Ionic bonds are very strong
bonds.
Formed between metal &
nonmetal atoms (elements).
Electronegativity difference
between the atoms is 1.7 or
greater. (see table on last page
of notes)
Ex) Na & Cl
Ionic Compounds:
 pack
into a pattern (crystal; lattice)
 have very high melting points.
Ionic Compound Cont…
 Dissolve
in water (H2O), and ions are then free to move
(dissociate).
 Conduct electric current.
Let’s Draw Some:

Do you remember how to draw a bohr model?
Draw one for Sodium and one for Chlorine

What do you think will happen?

Bond Diagrams
Ionic Bond-lose & gain
electrons
 Ex. NaCl

Lets make some Lewis Dot diagrams!!!



Draw a Lewis Dot for
Na & Cl.
Draw an arrow to show
what the electron will
do
Finally draw the ions in
the bond.
Let’s put it all together…
Lewis Dot Diagrams

Try some more…

Ca + O

Na + O
 Subscripts
= __________________________
Covalent Bonds (formed in molecular/covalent compounds)
Atoms are the basic unit. (atoms bond to form
them)
 Covalent bonds are firm, but molecules not
strongly held together.
 Force between atoms that share electrons.

Let’s draw some!


Remember covalent bonds SHARE electrons, so there
is no drawing arrows.
Ex- F2
Lewis Dot Diagrams…
Steps to help you…



Draw the lewis of each kind of atom in the
compound.
Highlight/circle which electrons will be shared
When you draw your molecule Draw
the center atom in the molecule with all 8 valence
electrons (use two “types” like x’s and o’s to show where
they came from)
 Draw in your other atoms and their valence electrons
 Circle each atoms’ “8 electrons”- they will overlap each
other where they share 
Ex- Cl2
Covalent/ Molecular Compounds:




Not packed into a pattern.
Have low melting points.
May not dissolve in water (H2O), but some can.
Do not conduct electricity; do not dissociate.
Kinds of Covalent Bonds

Can share different number of electrons:
Single- share ONE pair of electrons
 Double- share TWO pair of electrons
 Triple- share THREE pairs of electrons


Can be polar covalent or nonpolar covalent
bonds.
Polar vs Nonpolar Covalent Bonding
How do you know which type of bond
will form? Use two rules:



Calculation using electronegativity values on a periodic
table: (Note: if they are both/all metals, automatically,
it is a metallic bond!)
Subtract the values of the 2 elements (larger minus
smaller)
If difference is:
0-0.3 = nonpolar covalent bond
0.4-1.6= polar covalent bond
1.7 & up= ionic bond
Electronegativity Differences
summary…
If differenc is 1.7 & up
Electronegativities are so
great that one atom will
steal the electron away
0-0.3 difference
Electronegativities are the
same, so the atoms will
share nicely 
If difference is: 0.1-1.6
Electronegativities are not different
enough to steal the electron
away, but there will be a
“bully” who hugs the electrons
closer
A second way… “rule of thumb”

2) Periodic table/metal, nonmetal rule (Rule of
thumb):
 Metal
and Metal
= metallic bond
 Metal and nonmetal = ionic bond
 Nonmetal and nonmetal = covalent
 All
same nonmetal = nonpolar covalent bond
 Different nonmetals = polar covalent bond
Rule of thumb summary…
A metal with a nonmetal
Two Nonmetals
Both the same nonmetal
Two different nonmetals
Naming Rules:





Naming Chemical Compounds
Ionic Compounds:
Ionic compounds are formed when a metal atom
donates one or more electrons to a nonmetal atom.
This forms an anion and a cation. Which one is
which?
The metal will form a _______________.
The nonmetal will form a ________________.
Below are the rules for naming ionic
compounds:




1. Write the metal (cation) name first. (It does not
change)
2. Write the nonmetal (anion) name next but make
a slight change: Take off the end of the name and
add “–ide” instead.
Ex- Chlorine becomes “Chloride,” Oxygen
becomes “Oxide”
Covalent Compounds:






Covalent compounds are formed when two nonmetals share
electrons.
Rules 1. The first element is named first, using the elements name.
2. Second element is named as an Anion (suffix "-ide")
3. Prefixes are used to denote the number of atoms
4. "Mono" is not used to name the first element
Note: when the addition of the Greek prefix places two vowels
adjacent to one another, the "a" (or the "o") at the end of the Greek
prefix is usually dropped; e.g., "nonaoxide" would be written as
"nonoxide", and "monooxide" would be written as "monoxide". The "i"
at the end of the prefixes "di-" and "tri-" are never dropped.