Chemical Bonds

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Transcript Chemical Bonds

Chemical Bonds
Also Known As…
“The first rule of Fight
Club, is nobody talks
about fight club!”
Bond…Chemical Bond
A chemical bond is the term used to describe the
electrostatic attraction between pairs of atoms or ions.
When you look at an atom or ion, you will see that the
nucleus has all of the protons and neutrons while the
orbits/shells have the electrons.
Now if you picture two atoms or ions approaching one
another – it makes sense that “collision” point is going to
be the outermost orbit/shell of electrons.
These electrons in the outermost orbit of an atom or ion
are called the valence electrons and they are the first
line players in the bonding game. Their actions are going
to dictate the type of chemical bond that is formed
between the two atoms or ions.
The Octet & The Nobles Rule!
The octet rule states that atoms tend to form ions that have a full
outer electron shell. This configuration is known as a noble gas
configuration and it gives stability to the ion.
Even when atoms share electrons (as in the covalent bond) they
share only enough electrons to make their outer shells full to
capacity with electrons.
All electron shells/orbits are full when they have eight (8)
electrons in them – except for the first shell/orbit – it only needs
two electrons to fill it.
The important thing to know here is that there is a great deal of
stability associated with having a full outermost shell of electrons
– the way the Noble gases do.
You could think of it as if the other elements all want to become
full of electrons like the Nobles. The Nobles have it all and the
other elements are like peasants trying their best to become a
Noble. Nobles are stable so they don’t bond – they won’t risk
upsetting the balance of their full outer orbit of electrons.
Chemistry Fight Club!
Remember the term “electronegativity” – it’s the
“electron-grabbing strength” of an atom when it’s in a
chemical bond. It is going to help us decide what type of
bond will be formed between two atoms.
The more electronegative you are – the bigger an atomic
bully you are! If you are not very electronegative – you’re
a wimpy element waiting to get beat up.
When we determine what type of bond is going to be
formed between two atoms, we compare their
electronegativity values and see what is going to happen
in chemistry fight club tonight!
The types of bond that could be formed at chemistry fight
club are:
 The Ionic Bond
 The Covalent Bond
 The Polar Covalent Bond
Ionic Compounds
Bully beats wimp and steals toys!
Ionic compounds are substances that consist of
positive ions and negative ions held together by
electrostatic attractive forces. [Opposites attract]
Ions are formed when atoms lose or gain electrons. They
gain them or lose them as a result of chemistry fight
The nonmetal has a much greater electronegativity than
the metal so it simply beats the metal up and takes the
electrons its needs to become “Noble”.
The nonmetal gains electrons and become a negatively
charged ion. The metal loses electrons and becomes a
positively charged ion. Ironically, both the “bully” and the
“wimp” end up as “Nobles” as result of this electron
Ionic Bond Formation
Covalent Bonds
Two bullies share the toys!
Covalent bonds are chemical bonds that hold
nonmetals together through the sharing of pairs of
Nonmetals have high electronegativities – this can result
in two “bullies”, of very similar strength, fighting it out and
coming to a tie – so they agree to share the electrons
with each atoms donating one electron to the bond.
The nuclei of the atoms – full of positive protons – are
attracted to the shared pairs of electrons.
It is possible for two pairs of electrons to be shared
between two nonmetals – this results in a double bond.
If three pairs of electrons are shared – you get a triple
Covalent Bond Formation
Covalent vs. Ionic
Sharing vs. Taking
The Polar Covalent Bond
Bully and sidekick share toys unequally!
A polar covalent bond is the result of two nonmetals
sharing pairs of electrons in an unequal manner because
one of the nonmetals is stronger than the other
nonmetal. One has more “electron-grabbing strength”
than its partner but not enough to just rip them away.
The electrons tend to stay closer to the stronger atom
and therefore, it tends to carry a slight negative charge.
The weaker atom ends up with a slight positive charge.
This separation of charge within the same molecule is
known as a dipole.
Disney villains are great examples of polar covalent
relationships…Think of Gaston & Le Fou from Beauty
and the Beast – they both pillage and plunder the village
but when it comes time to reap the rewards – Gaston
gets the bigger take!
Polar Covalent Bond Formation
The Rules of Chemistry Fight Club
Obviously, the first rule of chemistry fight club is nobody talks
about chemistry fight club!
The second rule of fight club is…The type of bond that you
form with another atom depends on the difference between
your electronegativity values – this difference is known as the
ionic character.
Polar Covalent
To figure out the ionic character between two atoms, you
simply subtract the smaller electronegativity value from the
larger one.
3.0 – 2.1 = 0.9
Polar Covalent
3.0 – 0.9 = 2.1
3.0 – 3.0 = 0