On Earth, naturally occurring calcium metal contains 6 isotopes: Ca-40, Ca-42, Ca-43, Ca-44, Ca-46, Ca-48. Select all of the following that are true for a sample of naturally occurring calcium.

A) The average mass of the calcium atoms is 40.078 amu.
B)One mole of Ca-40 has a mass of 40.078 grams.
C)All of the calcium atoms have an atomic number of 20.
D)All of the calcium atoms have a mass number of 40.078
E) Some of the calcium atoms have a mass number of 40.
F)Some of the calcium atoms have a mass of exactly 42 amu.
G) One mole of the calcium atoms will have a mass of 40.078 amu.
H) It is likely that the most abundant isotope is Ca-40.
I chose A,B,C,E,G,H and can't figure out which ones I chose wrong. Thanks!

A is probably right but I don't there there is enough information there to know that. You must go to a periodic table to check it out.

I don't think B is right. The average of all of the isotopes is 40.078 but Ca-40 is not that mass.
C is ok.
D is not right. D would be ok if they said mass but not mass NUMBER. Mass number is the NUMBER of protons + NUMBER neutrons.
E is ok.
F is not right
G could be right but with no percentages given who knows. If you're given the periodic table you know it is right.
H probably is right but there isn't enough information in H to make sure; i.e., I know the atomic mass Ca is 40.078 which means most of the metal probably is 40, especially since there is no 41.

Let's go through each statement and determine which ones are true for a sample of naturally occurring calcium.

A) The average mass of the calcium atoms is 40.078 amu.
To calculate the average mass of naturally occurring calcium, you need to consider the relative abundance of each isotope and its respective mass. The average mass is calculated by summing the products of the isotope masses and their relative abundances. Given the isotopes and their abundances, the average mass of calcium is indeed 40.078 amu. Therefore, statement A is true.

B) One mole of Ca-40 has a mass of 40.078 grams.
This statement is partially incorrect. One mole of any element contains Avogadro's constant (6.022 x 10^23) of atoms or molecules. The molar mass of an element is the mass of one mole of atoms or molecules of that element. Since the atomic mass of Ca-40 is 40.078 amu, the molar mass of Ca-40 is 40.078 grams/mol. So, statement B is true.

C) All of the calcium atoms have an atomic number of 20.
The atomic number of an element represents the number of protons in the nucleus of an atom. Calcium has an atomic number of 20, meaning all calcium atoms have 20 protons. Thus, statement C is true.

D) All of the calcium atoms have a mass number of 40.078.
The mass number represents the sum of protons and neutrons in an atom. In this case, calcium has various isotopes with different mass numbers (40, 42, 43, 44, 46, and 48). Therefore, statement D is false.

E) Some of the calcium atoms have a mass number of 40.
This statement is true because there is an isotope called Ca-40, which has a mass number of 40.

F) Some of the calcium atoms have a mass of exactly 42 amu.
This statement is false. None of the naturally occurring calcium isotopes have a mass of exactly 42 amu.

G) One mole of the calcium atoms will have a mass of 40.078 amu.
This statement is false. One mole of calcium atoms will have a mass equal to the molar mass of calcium, which is 40.078 grams/mol, not 40.078 amu.

H) It is likely that the most abundant isotope is Ca-40.
This statement is true. The most abundant isotope of calcium is Ca-40, accounting for 96.941% of the naturally occurring calcium.

In summary:
Statements A, B, C, E, and H are true, while statements D, F, and G are false.