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>
More positive ions shows acidic whereas more negative ions indicates basic solution.
<h3>Which charge show acidic solution?</h3>
That side which has more positive charges is considered as acidic solution while on the other hand, that region where negative charges are present in large number as compared to positive charges is considered as basic or alkaline solution.
So we can conclude that more positive ions shows acidic whereas more negative ions indicates basic solution.
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Answer: Synthesis
Explanation: I think is suynthesis
The difference in the reactivity of metals accounts for why some metals will react with hot water but not with cold water. For example, aluminum is less reactive than sodium and will only react with hot water but not cold water.
<h3>What is reactivity of metals?</h3>
The reactivity of metals is the ability of a metals to lose electrons.
The reactivity of metals generally decreases from left to right across the periodic table but increases on going down a group.
Due to the differences in reactivity of metals, some metals are more reactive than others.
For example, the reactive metals sodium, potassium and calcium react with cold water to with differing degree of spontaneity to liberate hydrogen.
Some other metal like aluminum, zinc, and iron can only react with hot water or steam to liberate hydrogen.
Therefore, the reactivity of a metal will determine if it will react with cold water or hot water.
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