Examine the following isotopes of silicon (si).
silicon-28 (28si)
silicon-29 (29si)
silicon-30 (30si)
what is true about these isotopes?
they all have the same number of protons and neutrons.
silicon-28 and silicon-29 have the same number of protons and neutrons, but silicon-30 has a different number of neutrons.
they all have the same number of protons but different numbers of neutrons.
silicon-28 and silicon-30 have the same number of protons and neutrons, but silicon-29 has a different number of neutrons.

They all have the same number of protons but different numbers of neutrons.

Explanation:

These are called isotopes. Isotopy is the existence of two or more atoms of the same element having the same atomic number but different mass numbers due to the differences in the number of neutrons in their various nuclei.

The atomic number is the number of protons in an atom. For a neutral atom, it is the same as the number of electrons.

The mass number is the number of protons and neutrons in an atom.

silicon-28 (28Si)

silicon-29 (29Si)

silicon-30 (30Si)

All of these isotopes have an atomic number of 16

Now let us chech for the neutrons:

 Number of neutrons = mass number - atomic number:

for silicon-28 (28Si)  : 28-16 = 12 neutrons

     silicon-29 (29Si) :   29-16 = 13 neutrons

     silicon-30 (30Si):    20-16 = 14 neutrons.

mechanics (greek   is that area of science concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment. the scientific discipline has its origins in ancient greece with the writings of aristotle and archimedes[1][2][3] (see history of classical mechanics and timeline of classical mechanics). during the early modern period, scientists such as galileo, kepler, and newton laid the foundation for what is now known as classical mechanics. it is a branch of classical physics that deals with particles that are either at rest or are moving with velocities significantly less than the speed of light. it can also be defined as a branch of science which deals with the motion of and forces on objects. the field is yet less widely understood in terms of quantum theory.

explanation:

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of carbon is as shown here in the image.