# Homework Help: Basic Chemistry problem and I need help please!

1. Sep 13, 2011

### kelsie

The problem statement:

Complete the following table:

Symbol: Element Name: Atomic #: Mass # # of Protons # of Neutrons # of Electrons
34 Sulfur
S
16

I am confused how they got the # 34 above S. The atomic # is 16 and atomic weight is 32. How did they get 34?

Thanks!

2. Sep 13, 2011

### Staff: Mentor

You mean $^{34}S$? This is equivalent to $^{34}_{16}S$. Have you heard about isotopes?

3. Sep 13, 2011

### kelsie

Yes that's it. I don't get how they got the number 34. According to the web, Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons.

Is there a calculation they did to get that number?

Thanks!

4. Sep 13, 2011

### Staff: Mentor

There are several isotopes of sulfur, $^{34}_{16}S$ is just one of them. Mass can be determined (for example) by the mass spectroscopy, but it doesn't matter here. Question is about this particular isotope, regardless of where the information comes from.

5. Sep 13, 2011

### kelsie

wait I think I understand what you're saying. It's a given symbol so all I need to do is just plug it in the table that was given to me. Sorry chemistry is still new to me. How about the element Nickel? If the # of protons is 28 and # of neutron is 34, what is the symbol?

We are given a table to fill in the blank and I get the atomic #, protons, neutrons, and electrons. But confused about filling in the symbol part of the table.

6. Sep 15, 2011

### J-Girl

The atomic mass on the periodic table is simply just the most common ones. For example, carbon is usually the isotope(atomic mass) 12, but if it happens that there are more neutrons in that isotope, that will change the atomic mass. Protons will always be the same, but the number of neutrons in an element can vary. So in your table, they are asking how many protons/electrons/neutrons in THAT particular isotope of Sulfur. So just minus the atomic number of sulfur (which never changes on the periodic chart) from the mass number you are given, and that is how many neutrons are present in that isotope. Just remember that electrons do not hold a large enough mass to be counted, just count the neutrons and protons
:)

7. Sep 15, 2011

### Staff: Mentor

No, it is not the most common one. Element in nature is a mix of different isotopes, and the mass given in PT is a weighted average of their masses. Chlorine atomic mass is 35.5 - it doesn't mean the most common isotope has an atomic mass of 35.5, but the chlorine is an almost exactly 50/50 mixture of 35Cl and 36Cl.

8. Sep 15, 2011

### Staff: Mentor

What is the atomic mass of this isotope?