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INTERACTIVE MOLECULES -- SALT CRYSTALS

Why do table salt crystals have a cubic shape?


Ions of opposite charge strongly attract each other; those of like charges repel. As a result ions in an ionic compound are arranged in a particular manner. (Remember that an ionic bond is a bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other).

To form an ionic compound, there needs to be at least one metal and one non-metal. The metal element is usually the positive charge and the non-metal element is a negative charge. The arrangements of these atoms results in a regular, repeating arrangement called a crystal lattice. A crystal lattice gives the compound a great deal of stability. It also accounts for the high melting point of crystals. Read more about Salt (NaCl)

Note about 3D molecules -- Our files on this page now use Jsmol instead of Jmol. These files make use of Javascript which permits viewing of molecules on tablets, phones and easier use on Macs.Jsmol is best viewed with the Chrome browser.

 

 


What is Table Salt Made of?

Try this:

1)Click right mouse button-->Style -->Scheme--> Ball and Stick

3) Click the right mouse button over the image- Style --> Labels --> With Element Names

Rotate the Image using the left mouse button to view the different atom types.

What are the angle and distance measurements in a salt crystal?

Try this --

First label by atom names --- > Labels --> Atom Names

1) Measure the angle formed for Na11 --Na10--Na12

[Click the left mouse button twice over Na11 --> drag and click once on Na10 --> drag and click twice on Na12]

Please enter your answer in the space provided:


degrees

2) Measure the angle formed for Na9 --Na1--Na10

[Click the left mouse button twice over Na11 --> drag and click once on Na10 --> drag and click twice on Na12]


degrees.

3) What is the distance from Na11 to Na12?

[Double click on Na11 -- drag to Na12 and double click]


angstroms


Repeat for Na1 to Na10.


Ions of opposite charge strongly attract each other; those of like charges repel. As a result ions in an ionic compound are arranged in a particular manner. (Remember that an ionic bond is a bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other).To form an ionic compound, there needs to be at least one metal and one non-metal. The metal element is usually the positive charge and the non-metal element is a negative charge. The arrangements of these atoms results in a regular, repeating arrangement called a crystal lattice. A crystal lattice gives the compound a great deal of stability. It also accounts for the high melting point of crystals.

A chemical formula for an ionic compound shows the ratio of ions present in the crystal. In the case of sodium chloride the chemical formula is NaCl.

There are seven crystal classes: Cubic, Tetragonal, Orthorhombic, Monoclinic, Triclinic, Rhombohedral, Hexagonal


Multiple Choice Questions

1. What is the crystal class for NaCl?
a) Triclinic
b) Hexagonal
c) Cubic
d) Monoclinic

2. Salt has a high melting point because?
a) ionic compounds generally have high melting points
b) A crystal lattice gives the compound a great deal of stability
c) NaCl is rigid and tightly packed
d) all of the above

3. NaCl forms
a) covalent bonds only
b) ionic bonds only
c) both covalent and ionic bonds
d) there is no bonding formed in NaCl

4. Ionic compounds such as NaCl
a) dissolve easily in oil
b) have a low melting point
c) dissolve easily in polar liquids such as water
d) none of the above

5. Which of the following statements is not correct
a) Ionic bonds are formed between a metal and non-metal
b) Sodium is a metal and Chlorine is a non-metal
c) A sodium ion is negatively charged and a chlorine ion is positively charge
d) A sodium ion is positively charged and a chlorine ion is negatively charged


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