The atomic mass of arsenic is 75 atomic mass units; a neutral atom of asennic has 33 electrons. how many neutrons does arsenic normally have? a.33 b.42 c.75 d.108

42

Explanation:

Atoms have a neutral charge overall, which means they have an equal numbers of positively-charged protons and negatively-charged electrons. Here, an atom of arsenic with 33 electrons must also have 33 protons.

The mass of any atom is contained in its nucleus, a part made up of protons and neutrons - particles with no charge. Both protons and neutrons are exactly 1 atomic mass unit each, so to find the atomic mass of an atom, we can use the formula

(# of protons) + (# of neutrons) = atomic mass

or equivalently:

atomic mass - (# of protons) = (# of neutrons).

For arsenic, we have an atomic mass of 75 amu and 33 protons, so using our formula:

# of neutron = 75 - 33 = 42 neutrons

answer: a. a gene that causes a specific trait.

allowed for the prediction of the properties of missing elements.