Radioactivity or radioactive decay is the process that occurs when unstable isotopes or atoms release energy by emitting radiations such as ,gamma radiations, alpha radiations and beta radiations to attain stability. Therefore, in this case decay is likely to occur when a given atom has two many neutrons in its nucleus in order to attain stability.
Answer:
I think it is c
Explanation:
When water turns into water vapor it goes into the air so it must be lighter
Answer:

Explanation:
Number of molecules of water = 
= Avogadro's number = 
Number of moles is given by


The number of moles of water is
.
Answer:
<h2>ignore your body being cold</h2>
Hope it helps
The testable question which will provide evidence that elements in the same group have similar properties is valency
<h3>What is the valency?</h3>
In essence, how many electrons are present in their outermost shell.
Valency and Groups in the periodic table, elements are arranged in order of their atomic numbers and hence, the periodic table is a systematic arrangement of elements in an array of vertical columns called Groups and horizontal arrays called Periods.
which of the following testable questions will provide evidence that elements in the same group have similar properties A. Valency B. Orbit C. Group D. Period
Since, the reactive capacities of elements is dependent on the number of electrons on its outermost shell, we can conclude on this note that, Elements in the same group have similar properties.
Learn more on Groups and Valency:
brainly.com/question/1645905