Which of the following statements about elements is not true? A. Elements contain equal numbers of protons and electrons.
B. Elements contain equal numbers of neutrons and electrons.
C. Elements contain protons and neutrons in their nucleus.
D. Elements contain electrons that orbit around the nucleus.

According to the statements of your question, the answer is B: elements contain equal numbers of neutrons and electrons.  

To find the correct answer, we must evaluate each statement.

A. Elements contain equal numbers of protons and electrons

It is correct. In a neutral atom, the number of protons and electrons is the same. When an atom gain or lose electrons, the number of electrons is bigger (the atoms gain electrons) or lower (the atoms lose electrons) than the number of protons.          

B. Elements contain an equal number of neutrons and electrons.

It is false. The nucleus of an atom is composed of neutrons and protons, where the atomic mass is given by:

Where:

Z: is the number of protons = atomic number

N: is the number of neutrons

The difference between the numbers of neutrons, protons, and electrons is evidenced in the so-called isotopes. These are atoms of the same element that have the same number of protons (and hence the same number of electrons if the atom is neutral) and a different number of neutrons in the nucleus.

An example is the hydrogen element, whose isotopes are protium (¹H), deuterium (²H), and tritium (³H). In all of them, the number of protons and electrons is the same (equal to 1), the number of neutrons is 0, 1, and 2, respectively, and the atomic masses are 1, 2, and 3, respectively.                  

C. Elements contain protons and neutrons in their nucleus.

It is correct. According to Rutherford's atomic model, the nucleus of an atom is composed of protons and neutrons with electrons moving around the nucleus.      

D. Elements contain electrons that orbit around the nucleus.

It is correct.  As we said earlier, Rutherford's atomic model states that negatively charged electrons move in circular paths around a positively charged nucleus. Later, Bohr proposed an atomic model based on circular paths with discrete energy values.        

You can find more about the atomic model here:

I hope it helps you!

Option A is not true

Explanation:

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put the answers   and i could answer.

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.