Molecule Shape and Polarity Flashcards

Flashcards covering molecule shape, polarity, and intermolecular forces based on lecture notes.

What is molecular polarity?

A measure of the uneven distribution of electrons in a molecule, resulting in partial positive and negative charges.

How does a gecko walk upside down on a ceiling?

A gecko has many tiny hairs on its foot that polarize ceiling molecules, causing the hairs and ceiling to attract one another electrostatically.

How does cling-wrap cling to glass?

Cling-wrap molecules polarize glass molecules, causing the two to attract one another electrostatically.

Why doesn’t food stick to Teflon?

Teflon is a non-polar substance, so it does not form strong electrostatic bonds.

Why doesn't fat dissolve in water?

Fat is non-polar, while water is polar, therefore they don’t dissolve in one another.

How does soap help clean fatty plates?

Soap has a polar and a non-polar end, enabling it to bond with fat and with water, ‘bridging the two’, thus making the fat dissolve in the water.

What is the difference between an intramolecular bond and intermolecular force?

One chemical (intramolecular) bond: is always between two atoms and involves two electrons. One intermolecular force: is always between two molecules.

Why would two molecules attract one another?

Because one end (pole) of the molecule is more positive than the other (which is more negative than the other).

When do molecules attract one another electrostatically?

Molecules attract one another electrostatically if they have positive and negative poles (are polar or can be polarised).

What is a polar molecule?

If as a whole a molecule has a ‘+ end’ and a ‘– end’, it is called a polar molecule.

What is the difference in electron sharing between H2 and HF molecules?

H2 shares electron pair equally between H and H. HF shares electron pair unequally because F pulls pair stronger than H.

What must be true for a molecule to be polar?

Bond polarity is a necessary but not sufficient condition. Molecular geometry must also result in an asymmetrical distribution of charge.

What is the VSEPR model used for?

To determine the shapes/symmetry of some molecules.

What are non-polar molecules with non-polar bonds?

Diatomic molecules such as H-H. ∆EN: 2,1-2,1 =0

What is the condition that makes CO2, BF3, CCl4 non-polar molecules with polar bonds?

If there is no resultant dipole in the molecule, the shape of the molecule is symmetrical even with polar bonds.

What is the angle of linear molecule?

180 degrees

What is the angle of trigonal planar molecule?

120 degrees

What is the angle of Tetrahedral molecule?

109˚28’

What is necessacry for a molecule polarity with a linear molecule?

Electronegativity difference between bonding atoms > 0. Unequal sharing of electrons leading to a resultant dipole forming in the bond and molecule. The shape of the molecule is asymmetric or non-polar

Describe Trigonal Pyramidal polar molecules

1 lone e- pair repel bonding pair more. 3 bonding e- pair repel each other. Also Is Asymmetrical and Polar molecules examples NH3 which gives a net dipole

Describe Angular polar molecules

2 bonding pairs at an angle less than 180º, and two lone e- pairs on the central nucleus.Polar bonds. repel repel repel

When are molecules containing polar bonds non-polar?

If the polar bonds are arranged symmetrically, the partial charges cancel out and the molecule is non-polar.

When are molecules containing polar bonds polar?

If the polar bonds are arranged asymmetrically, the partial charges do not cancel out and the molecule is polar.

Give three examples of molecular shapes and symmetry

Linear, Trigonal Planar, Tetrahedral

What are the conditions for molecule polarity of asymmetrical shapes?

Inside & outside ∆EN > 0, this yields a dipole