I believe the correct answer from the choices listed above is the last option. The term that would best describe the <span>role of hydrogen gas in the formation of a water molecule would be a reactant. Water has a formula of H2O where it contains water so it should be that hydrogen is a reactant. </span>
B is the answer
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It expresses a cube using cm
Answer:
is a way of presenting information about the chemical proportions of atoms
Explanation:
Answer:
A. there is an isotope of lanthanum with an atomic mass of 138.9
Explanation:
By knowing the different atomic masses of both Lanthanum atoms, we can not tell anything about their occurence in nature. Therefore, all the last three options are incorrect. Because, the atomic mass does not tell anything about the availability or natural abundance of an element.
Now, the isotopes of an element are those elements, which have same number of electrons and protons as the original element, but different number of neutrons. Therefore, they have same atomic number but, different atomic weight or atomic masses.
Hence, by looking at an elements having same atomic number, but different atomic masses, we can identify them as isotopes.
Thus, the correct option is:
<u>A. there is an isotope of lanthanum with an atomic mass of 138.9.</u>
