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>
Answer:
0.607mol
Explanation:
n(AR) = mass / molar máss
= 24.3 /40
=0.607
Answer:
Explanation:
6. When insulating materials rub against each other, they may become electrically charged .
7. Charging by conduction involves the contact of a charged object to a neutral object.
8. Grounding is the process of removing the excess charge on an object by means of the transfer of electrons between it and another object of substantial size.
9. Grounding is the process of removing the excess charge on an object by means of the transfer of electrons between it and another object of substantial size.
