6. how is the number of neutrons in the nucleus of an atom calculated?

By substracting the atomic mass by the number of protons.

here is an example sodium's atomic mass is 23,
it is given that the number of protons is 11. Find the number of neutrons.

easy substract 23 from 11. the answer is 12 neutrons.

For the answer to the question above, you must first calculate the no. of Neutrons. Then, subtract the atomic number from the atomic weight. The result of that is the number of a neutron.The atomic number is the number of protons. The atomic weight consists of the number of protons plus the number of neutrons. I hope my answer helped you

For cyclohexane compounds drawn in a chair conformation:   -axial bonds are vertical  -equatorial bonds are parallel to two bonds within the ring.  thus, as i assume the chair conformation is drawn:   -the x group is in an axial position, as are the five other vertical bonds.  -three axial bonds are on the top face of the ring  -the other three axial bonds are on the bottom face  the position of the second substituent on each ring carbon is equatorial.  gauche groups must be on an adjacent carbon such as carbon 6 and carbon 2, and also gauche groups are rotated by 60 degrees relative to each other.  drawing the newman projections for c1–c2 and c1–c6 aids in visualizing the groups that are gauche to the y group on c1.  click this link and watch some academic videos that may you more understand the topic 

Well to my expert knowledge and my exquisite calculations i think the the negative ion # 412 is the key to sucess