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Answer:</h2><h2>The primary requirement for good melting point determination is that the sample be in a fine powder form. This makes the heat transfer into the sample more efficient and reproducible, and also enhances the overall reflectivity of the sample for easier automated detection of the melt</h2><h2 />
halogens
Group 7A (or VIIA) of the periodic table are the halogens: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).
We know, by law of constant proportion :
Chemical compounds always contains its component in constant fixed ratio or in fixed percentage without depend on its source, method of preparation and mass of compound.
Therefore, percentage of oxygen is same for any mass.
Hence, this is the required solution.
A. Atoms. Because I learned this in 6th grade.