Chlorine has an average atomic mass of 35.45 atomic mass unit. the to naturally occording isotopes are Chlorine-35 and Chlorine-37 Why does this indicate that most chlorine atoms contain 18 neutrons?

Answer 1

This has to due with the abundance of each. Lets break it down for a moment.

The mass number is the sum of the number of protons and the number of neutrons. All chlorine atoms have 17 protons, so if we so a little subtraction, we can find out that there are 18 neutrons in 35Cl (Chlorine-35) and 19 neutrons in 37Cl. Another important piece of information that we need to know is that the Atomic Mass is an average of its isotopes. So lets say that there are equal amounts of 35Cl and 37Cl (50% of each). If we calculated the atomic mass (the average of the two), we would get a number that's directly in-between 35 and 37 since they are found in equal amounts in nature. Then the atomic mass would be 36.

But we know this isn't true. There are not equal amounts of each isotope in nature; therefore, the atomic mass will not fall directly between the two masses of isotopes. The atomic mass of chlorine is 35.45, which means one isotope is more abundant than the other. Since 35.45 is closer to the weight of 35Cl, we know there is more of that isotope than 37Cl. Then, because we already figured out that there are 18 neutrons in 35Cl, we can officially say that most chlorine atoms have 18 neutrons.

Answer 2

Most chlorine atoms contain 18 neutrons because:

The atomic number of Chlorine is 17 - indicating the number of protons found in the atomic nucleus. Seeing as the atomic mass is 35, we subtract the number of protons from 35 to get the number of neutrons, 18.

We test our equation: 17 protons + 18 neutrons = 35

Chlorine-35 is the most common natural occurring isotope of chlorine which is why most chlorine atoms contain 18 neutrons.

Answer 3

The atomic number of chlorine is 17 Both isotopes therefore have 17 protons and 17 electrons Cl 35 has 18 neutrons while Cl 37 must have 20 neutrons

Answer 4

The Cl-35 isotope is more abundant, because the average atomic mass is closer numerically to 35 than to 37.

Answer 5

Yes, it does.