SABIS Grade 11 - Year 2021/2022 Chapter (9) Level M Chemistry ~ K Chemistry ®

Bonding in Solids and Liquids

Part 1

ALL molecules have polar bonds (dipoles) EXCEPT elements

Applications:

1. Specify the major intermolecular forces that exist in a crystal of each of the following elements:
a) Ne
b) Cl₂
c) K
d) F₂
e) Xe
f) C (diamond)
g) Al
2. Specify the major intermolecular forces that exist in a crystal of each of the following compounds:
1) CCl₄
2) CO₂
3) NH₃
4) PH₃
5) HCl
6) NaCl
7) HF
8) CS₂
9) CH₄
10) SiO₂
11) HBr
12) HI
13) NaOH
14) CaI₂
15) SiO₂
16) C₂H₅OH

Part 2

 Strength of bonds:

1) Hydrogen bond > dipole – dipole > VDW
Stronger stronger

2) Ionic bond

molecular bond
(covalent bond > hydrogen bond >

dipole-dipole > VDW)

 Compare melting points / boiling points of elements using strength of intermolecular forces Compare hardness of given elements according to strength of IMF  Compare melting points / boiling points of compounds using strength of intermolecular forces

Which has a higher boiling point HF or HCl? Why? Explain states of given substances using strength of IMF Explain variation in boiling points between given substances using strength of IMF

 The Importance of Hydrogen BondingHydrogen bonding is also extremely important in biological systems. For example the two strands of
DNA (deoxyribonucleic acid) are held together entirely by hydrogen bonding.

Part 3

Inter- and intramolecular hydrogen bonds.Some molecules, as a consequence of their shape, can form intramolecular (within the molecule
itself) hydrogen bonds. For example two isomers of butenedioic acid (HOOCCHCHCOOH): maleic
and fumaric acids have the same formula but because of the rigid double bond only maleic acid can
form an intramolecular hydrogen bond

The intramolecular hydrogen bond means that one of the hydrogen atoms (the intramolecular hydrogen bonded one) is especially stable.
If one H+ is lost the remaining O- is stabilized because its negative charge is attracted to the δ+ of
the hydrogen in the hydrogen bond. Consequently the first proton is lost easily from maleic acid, the
second is very hard to remove. Fumaric acid cannot form intramolecular hydrogen bonds so it is
harder to remove the first proton (the O- is not stabilized) but easier to remove the second.

Part 4

Factors affecting the strength of VDW

1) Number of electronsThe larger the number of electrons in a molecule, the stronger the VDW.2) Molecular shape
More symmetry means higher melting points, but lower boiling points.

see example

Part 5

II. Intramolecular Forces of Attraction Types of Crystalline Solids1. Ionic solids(Ions occupy lattice points, example Sodium chloride)
2. Molecular solids(Discrete covalent molecules occupy lattice points. Example: ice and sucrose)
3. Atomic Solids (pure elements)a) Metallic solids
b) Network solids
c) Group 8A solids

1. Ionic Bond:
 Definition:It is the strong electrostatic force of attraction between positively charged ions (cations) formed by metals and negatively charged ions (anions) formed by non-metals.

 Properties: SQ15, BQ11, 12, 151) Hard crystalline solids
2) Have high melting point and boiling point (due to strong electrostatic force of attraction between
oppositely charged ions).
3) Soluble in water (as water molecules are able to bind with positive and negative that make up the
lattice).Lattice is a regular pattern of positive and negative ions.4) Do not conduct electricity when solid but conduct electricity when molten or aqueous.When solid, ions are not free to move and carry electric current, but when molten or in aqueous
solution, ions are free to move and carry electric current.5) Brittle. Uses:As electrolytes, since they conduct electric current when molten or aqueous.

2. Covalent Bond: Definition:It is the equal sharing of one or more pair of electrons between two non-metal atoms. Properties:1) They are gases or volatile liquids or low melting point solids.
2) Have low melting point or boiling point due to weak VDW forces between the molecules
although they have strong covalent bonds between the atoms.
3) Insoluble in water but soluble in organic (most covalent compounds are non-polar)

4) Insoluble in water but soluble in organic solvents.

5) Do not conduct electricity when molten or in aqueous solutions (because they do not have ions
that can move and carry electric current

 Solubility of electrolytes in water
Hydration is the process whereby, in polar solvents such as water, positive and negative ions can be
stabilized or ‘hydrated’ by the attraction of the ion to the part of the solvent molecules which have
the partial opposite charge.
For example, you will recall that the water molecule has a partial negative charge on the oxygen and
partial positive charges on the hydrogens. When an electrolyte such as NaCl is dissolved it splits up
into ions. The Na+ is hydrated by being surrounded by the partial negative charged oxygen atoms of
water whereas the Cl- is surrounded by the partially positively charged hydrogens of water. This
attraction between oppositely charged species lowers the overall energy and the electrolyte will
dissolve.
In non-polar solvents such as CCl4 this hydration is not possible and electrolytes do not dissolve very
well or dissociate in non-polar solvents.

3. Metallic Bonding Definition:It is the electrostatic force of attraction between the mobile sea of electrons (delocalized electrons)
and the regular array of positive metal ions within solid metal. This simplest unit is a cation.

 The structure of a typical metalIt is formed of cations (positively charged particles) made of the nucleus and the inner shell
electrons. Between the cations there is a sea of pouter electrons which are shared by all atoms and
can move anywhere forming a mobile sea of free electrons (delocalized electrons)

 Properties