Why is it necessary to use models to study submicroscopic objects such as atoms and molecules? a. these objects do not exist in the real world. b. these objects are too far away to observe. c. these objects are too small to see. d. these objects can only be described mathematically.

The answer is C. These objects are too small to see.

The answer is: C. These objects are too small to see.

For example, ball and stick model gives informations about bond lenght and space filling model gives information about space occupied by atoms.

In chemistry, the ball-and-stick model is a molecular model of a chemical substance which is to display both the three-dimensional position of the atoms and the bonds between them. The atoms are represented by spheres, connected by rods which represent the bonds. Every ball represent one atom in one molecule and they have different colors for different atoms (for example, carbon is black, hydrogen is white, nitrogen is blue).  

There also other models: skeletal models, polyhedral models, composite models, computer-based models.  

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

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