The answer is a , as aluminium has 13 protons and electrons .
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: i’m pretty sure it’s 560 sorry if I'm wrong but can I get brainlest
Explanation:
Independent Variable: amount of sunlight given
Dependent Variable: How tall the plants grow
Control: The plant given no sunlight
Molar mass H₂SO₄ = 98.0 g/mol
Volume = 1.290 L
number of moles:
153.3 / 98 => 1.564 moles
M = n / V
M = 1.564 / 1.290
M = 1.212 mol/L
hope this helps!