1) The document discusses molecular geometry and polarity. It defines molecular geometry as the three-dimensional arrangement of atoms in a molecule.
2) Lewis electron dot structures are used to represent valence electrons around atoms. The octet rule states that atoms gain, share, or transfer electrons to achieve a stable 8 electron configuration.
3) Valence shell electron pair repulsion theory predicts molecular shapes based on the number of bonding pairs and lone pairs around a central atom. Symmetric shapes are nonpolar while asymmetric shapes are polar due to unequal electron sharing.
4. Lewis Electron Dot Structure (LEDS)
• The valence electron are represented using dot around the
symbol of the element.
OXYGEN
1
2
3
4
5
6
6 valence electron
5. O
The symbol of the element that represents the nucleus of the atom
O
9. WATER MOLECULE
Octet Rule: States that atoms tend to gain, share or transfer electron in
order to attain a stable 8 valence electron configuration
LONE PAIR
BONDING ELECTRON
H
10. Lewis Dot Structure of Water
H
H
BOND PAIRS
OXYGEN = 2 LONE PAIRS
HYDROGEN = 0 LONE PAIR
11. Lewis Dot Structure of Ammonia
N
H
H
H
NITROGEN = 1 LONE PAIR
HYDROGEN = 0 LONE PAIR
BONDING PAIRS?
3
12. To predict the shape of the
Molecule
Valence Shell Electron Pair Repulsion (VS
Theory
Key ideas of the VSEPR:
1. Electrons pairs stay as far apart from each other as possible to
minimize repulsions.
2. Molecular shape is determined by the number of bond pair and
lone pairs around the atom.
3. Treat multiple bonds as if they were single bonds. (in making
prediction)
4. Lone pairs occupy more volume than bond pairs
13. NOTE: Remember the arrangement of the specific number of electron pairs
and its corresponding VSEPR shape
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21.
22. Predicting the Shape of the Molecules
Count the number of
electron pairs around
the central atoms
1 2
3
4
4 Electron
pairs:
2 lone pairs
2 bond pairs
23. Predicting the Shape of the Molecules
Determine the
molecular geometry or
the VSEPR shape
BENT
2 Bond pairs
2 Lone pairs
24. Determining Polarity Using Molecular
Geometry
• Non – Polar molecule – if the shape of the
molecule is symmetrical.
equal sharing of electrons.
No dipole moment.
Valence electrons are shared equally on both
sides of an atom.
29. POLAR MOLECULE
•If the shape of the molecule is
asymmetrical.
Unequal sharing of electrons
between atoms.
Has dipole moment (partial positive
and negative)
Molecular Geometry – by simply looking at the shape
Understanding the molecular structure of a compound can help you determine the polarity of a molecules
Understanding the molecular structure of a compound can help you determine the polarity of a molecules
Understanding the molecular structure of a compound can help you determine the polarity of a molecules
A metalloid is a type of chemical element which has a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals.
Alkali metals - The alkali metals are so called because reaction with water forms alkalies (strong bases capable of neutralizing acids)
Alkaline earth metals - the second most reactive family of elements because they readily give up their two valence electrons to achieve a full outer energy level, which is the most stable arrangement of electrons.
Transition elements - They are typically metals with a high melting point.
Understanding the molecular structure of a compound can help you determine the polarity of a molecules
If there 2 electron pairs bonded to the central atom and the central atom has no lone pair. The arrangement of electron pairs form a linear shape (180°)
3 electron pairs bonded to the central atom and the central atom has no lone pair.
When there are 2 bond pairs and the central atom has 1 lone pair
If there are 4 electron pairs bonded to the central atom and the central atom has no lone pair
NO LONE PAIRS AT THE central atom
Therefore, Hydrogen is attracted to Chlorine and fluorine
The central atom has lone pair, making them unequal although the molecules are a linear shape