How do I calculate the neutrons electrons and protons of these?

I figured out that calcium has 20 of each, but then how do i calculate these? Can you please explain how these work?

Calculate protons, neutrons and electrons of Ca 2+

Calculate protons, neutrons and electrons of Cl 1-

Calculate protons, neutrons and electrons of Ca -41

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• 10 years ago

You can determine the number of protons and electrons without difficulty, but you can never determine the number of neutrons based on the information provided. There are four stable isotopes of calcium. The most abundant is calcium-40. All isotopes of the same element have the same number of protons, but different numbers of neutrons. In order to determine the number of neutrons, you must specify the isotope by giving its mass number.

The ionic charge tells the number of electrons gained or lost. Since electrons are negative, adding an electron will make the ion have a negative charge, and losing electrons will make for a positively charged ion.

A calcium(II) ion, Ca2+, has 20 protons and 18 electrons because it has lost two (to give it the +2 charge). Again, it's impossible to say how many neutrons.

Chloride ion has gained 1 electron, and therefore, has 17 protons and 18 electrons, and again, it's impossible to say how many neutrons without specifying the mass number of the chlorine isotope.

Finally, you've specified an actual isotope. Calcium-41 has 20 protons, 20 electrons and 21 neutrons. The mass number, 41, is the sum of the protons and neutrons.

The Skipper says, "Neutrons = atomic weight - atomic number = 40-20 = 20 neutrons." This is what Gilligan might say, and it's wrong. You can't determine the number of neutrons unless you know the mass number for the particular isotope. The "atomic weight" is NOT the mass number.

And this is even worse: "Cl neutrons = 35.453 - 17 = 18.453. Can't have a non-integer number of neutrons so Cl must be a mixture of isotopes."

Of course its a mixture of isotopes. That is where the 35.453 amu comes from. It is the WEIGHTED AVERAGE of all of the naturally occurring isotopes of chlorine. 35.453 amu is NOT the number of protons and neutrons. The mass number is the number of protons + neutrons and it is a whole number, a counting number, an integer because it COUNTS the number of particles in the nucleus.142

• 10 years ago

Atomic number of Ca = 20 and the atomic weight = 40.08

Protons = atomic number = 20 protons

Neutrons = atomic weight - atomic number = 40-20 = 20 neutrons

Ca has 20 electrons (electrons equal protons in a neutral element)

Ca^+2 has lost 2 electrons; 20 - 2 = 18 electrons

Ca 41

20 protons and 20 electrons

41 - 20 = 21 neutrons

Cl atomic number = 17

Cl protons = 17

Cl^-1 electrons = 17 + 1 = 18 electrons

Cl neutrons = 35.453 - 17 = 18.453

Can't have a non-integer number of neutrons so Cl must be a mixture of isotopes

Cl 35 (18 neutrons) and Cl 37 (20 neutrons) are the 2 stable isotopes (approximately 77% Cl 35 and 23% Cl 33)

• Anonymous
10 years ago

The proton number is always going to be the atomic number. The number of neutrons is variable from isotope to isotope but it equals the mass number (given to the left of each element) minus the atomic number. Finally, the number of electrons is the same as the atomic number of a neutral element. Therefore, if you have an ion, simply add or subtract the oxidation number of the element from the atomic number to get the total number of electrons; you add if the charge is negative and you subtract when the charge is positive.

In the examples you have been given above, the number in front of the elements Ca2+ and Cl- represents the charge of the molecule, whereas in the third one it represents the mass number and the atom is neutral. Since you're not given the mass number for the first two, the safest thing to do is to determine the number of neutrons of all the stable isotopes of Ca and Cl; these are:

Ca-40, Ca-42, Ca-43, Ca-44, Ca-46, and Ca-48

Cl-35 and Cl-37

So, let's begin:

Number of protons = atomic number:

Ca = 20

Cl = 17

Number of electrons:

Ca2+ = 20 - 2 = 18

Cl- = 17 + 1 = 18

Ca = 20

Number of neutrons:

Ca-40 = 40 - 20 = 20

Ca-41 = 41 - 20 = 21

Ca-42 = 42 - 20 = 22

Ca-43 = 43 - 20 = 23

Ca-44 = 44 - 20 = 24

Ca-46 = 46 - 20 = 24

Ca-48 = 48 - 20 = 28

Cl-35 = 35 - 17 = 18

Cl-37 = 37 - 17 = 20

Hope this helped you out.