The element calcium has the atomic number of 20 and the mass number of 40, how many neutrons does it have?

Question

Jose Ayala · Accepted Answer

undefined Calcium has 20 neutrons.

Serenity Allen · Answer

20

There aren't many easy guidelines to abide by. (1) The number of protons equals the atomic number. #Z# = number of protons (2) The number of protons and electrons in an element with neutral charge is equal. #Z# = number of protons = number of electrons (no charge) If not, a positive charge indicates an electron loss and a negative charge indicates an electron gain for the element. (3) The total number of protons and neutrons makes up the mass of an atom. #A# = number of protons + number neutrons or #A# = #Z# + number neutrons So if you say that #Z# = 20 and #A# = 40, then #A# = #Z# + number neutrons 40 = 20 + neutron count 40 - 20 = neutron count Consequently, 20 neutrons in total

Natalie Anton · Answer

An atom of the calcium-40 isotope has #20# neutrons in its nucleus.

The mass number of an isotope is the total of the protons and neutrons in the atomic nucleus; the atomic number is the number of protons. Isotopes are named according to their mass numbers, for example, carbon-14. The calcium-40 isotope has a mass number of #40#, and an atomic number of #20#, therefore it has #20# protons. #"Number of neutrons"="(mass number)"-"(atomic number)"# #"Number of neutrons"=40-20=20#