The table below gives the numbers of protons, electrons, and neutrons in four atoms.
atom
number of protons
number of neutrons
number of electrons
based on the table, which atom has a charge of -1?
o1
o2
o3
04

Explanation:

The molar volume of an ideal gas is given by the formula Z =PV/nRT, since we are asked about the temperature and Pressure sincere P is the pressure and T is the temperature and when both are low the overall Z for the ideal gas will become low let it be Z’ and suppose volume of real gas is given by Z1.  

Then if previously the ratio was Z/Z1  under low temperature and pressure the new ratio would be Z'/Z1 and this ratio would be smaller than the previous ratio.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.