# What determines the number of neutrons

## Calculate the number of neutrons Homework solutions
from experts Hello and how do you calculate the number of neutrons of an element I always get 21 out of eg Ca but I wrote down 24 ?? The mass number is calculated less than the ordinal number  The atomic number tells you how many electrons are in the element. The number of protons and electrons are the same because the element is charged. 24 is the mass number of magnesium. How do you get to 21 at Ca? Yes, you don't count at approx. 41-20 And that gives 21 as the number of neutrons And what is the difference between mass number and atomic mass The number of mass and atomic mass of elements are the same. Can't be correct mass number is at Ca 44 and atomic mass is 40 The element Ca has a mass number of 40.078g / mol. if you look at the periodic table. With the mass number 44 there is an isotope of Ca, then there are 23 neutrons.  Yes, if you calculate the mass number minus the atomic number, that is 44-20, you get 24 neutrons But you can also calculate 40-20 and 42-20 etc. that there are also mass numbers, it always comes out with a different number of neutrons The rounded mass number and atomic mass are roughly the same because the mass of the protons is not exactly 1. Isotopes of an element differ in the number of neutrons. Therefore one always gives an element with atomic number and mass number so that one knows whether one is talking about the element or the isotope. Yes ok so my statement above is correct that there are isotopes with 22, 24 etc. neutrons Ca has three isotopes with mass numbers 40, 42 and 44 and the corresponding neutrons 20, 22 and 24 When everything is cleared up, please close the question. Thanks! So if the professor were to ask me how many neutrons Ca has the possible correct answers would be 20, 22 and 24? It actually has to give the mass number because of the isotopes. If you give all three numbers, you have to mention the isotopes. When you only talk about Ca you usually only mean the element with 40. Therefore, I was not able to assign the number 24 correctly immediately. I'm a chemist, but I don't know all isotopes by heart either ;-) So excuse me for asking so many questions, but I just want to be sure .... Mass number = number of nucleons and the teacher has to specify this so that I can calculate the neutrons and when you talk about Ca I have to calculate 40-20 which comes to a neutron number of 20 ? It's okay with the questions. Like to help. Yes now it is right. if it is past now, please close the question! thanks Please close the question, thank you   ### Tuition with a guarantee of getting through

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