1) Lewis dot structures (also called electron-dot formulas) represent how valence electrons are arranged between atoms in a molecule using dots to represent electrons. 2) Atoms bond by either sharing or transferring electrons to achieve stable electron configurations like noble gas structures. 3) Ionic bonds form when electrons are transferred from a metal to a nonmetal, while covalent bonds form when electrons are shared between atoms.

1. Chemistry 11
Chemical Bonding
TOPIC – LEWIS DOT STRUCTURE
BY – GUNJAN AGARWAL

2. Chemical Bonding
Electronegativity – the tendency of an atom
to attract electrons from a neighbouring
atom.
Hey! I
find your
electrons
attractive!
Get
lost,
loser!

3. Electronegativity increases as you move from left to right.
Electronegativity
decreases
as
you
move
down
each
column.

4. Valence Electrons – electrons in the
outermost occupied energy level. (s and p
electrons outside the core)
Valence electrons can be represented by
“dots” drawn around the atom.

5. Gilbert Newton Lewis
Invented “Electron-dot”
formulas or “Lewis
Structures”
I’m so tired of writing
all those useless inner
electrons, in the
Bohring models!

6. When the electronegativities of two atoms are
quite different from each other:
One atom loses an electron (or electrons)
The other atom gains an electron (or electrons)
This results in an Ionic Bond.
Chemical Bonding (Choose Ionic Bonds)
crystal lattice viewer

7. NaCl
Crystal Lattice

8. Li F
Li F
A Li Atom An F Atom
A Li+ Ion
-
+
An F- Ion

9. Be F
Be F
A Be Atom An F Atom
A Be2+ Ion
-
2+
An F- Ion
F
An F Atom
F
An F- Ion
-

10. The melting points of some Ionic
Compounds are as follows:
NaF 993 oC
KCl 770 oC
LiCl 605 oC
These high melting points are
experimental evidence that Ionic Bonds
are VERY STRONG. (Hard to break just
by heating).

11. When Electronegativities of bonding atoms
are the same (as they are in diatomic
molecules) or close to the same, they
SHARE electrons.
Bonds formed when atoms share electrons
are called Covalent Bonds.
In diatomic molecules (like H2 or Cl2), the
electronegativities of both atoms are
exactly the same so electrons are shared
equally!
Covalent Bond animation

12. In Covalent bonds, electrons
are Shared

13. H H

14. Lewis Structures (Electron-dot formulas)
for Ionic Compounds.
Remember, in an ionic compound, the
metal loses e-’s and the non-metal gains.
There is no sharing. Here is the e-dot
formula for sodium chloride (NaCl)
Na+
Cl

15. Here is the e-dot formula (Lewis Structure)
for the ionic compound MgF2 :
Mg2+ F
F
Notice, there is no sharing. The F atoms
took both valence e-’s from Mg, forming
ions which do not share electrons. The +
and – charges on the ions cause them to
attract each other.

16. Electron-dot Formulas (Lewis Structures)
for Covalent Compounds.
When atoms form covalent bonds, they
are trying to achieve stable noble gas
electron arrangements:
Hydrogen will share e-’s until it feels 2 e-’s
like Helium.
Other elements share e-’s to achieve what
is called a “Stable Octet” (8 valence e-’s)

17. Electron-dot formula for Methane (CH4)
C
H
H
H
H
Here is a Carbon
atom (4 val e-’s) and
four Hydrogen
atoms (1 val e- each)

18. Electron-dot formula for Methane (CH4)
C
H
H
H
H
Now they have
formed a stable
molecule. Each
C atom “feels”
like it has a
stable octet.
Each H atom
“feels” like a
stable “He”
atom with 2e-s

19. Electron-dot formula for Ammonia (NH3)
N
H
H
H
Here is a Nitrogen
atom (5 val e-’s) and
three Hydrogen
atoms (1 val e- each)

20. Electron-dot formula for Ammonia (NH3)
N
H H
H
“N” now
feels like it
has a stable
octet
Each “H”
feels like it
has 2 e- like
Helium.

21. Write the electron-dot formula for CF4
C
F
F
F
F
Because “F” is a
halogen, it has 7
valence e-s, so
you must show
all 7 red dots
around each
“F” atom!

22. Write the electron-dot formula for H2S
S H
H
The two H’s
MUST be at
right angles to
each other!!

23. Write the Electron-Dot Formula for SeF2
Because “F” is in
Group 17, they have
7 valence e-s, so they
must have 7 red dots
around them.
Se F
F