Answer:
the number of protons in the nucleus of an atom. the number of protons define the identity of an element
Answer:
Explanation:
A substance melting is a physical change and the properties of the substance will remain same, only that the substance will just become liquid.
On the other hand, burning is a chemical change which produces an entirely new compount(in most cases, ash) which does not have the same properties as the original object
Answer 1
The sample will dissolve in more than 1 minute.
Explanation :-
Generally Solubility and rate of solubility of substances increase with the increase in temperature. So lower the temperature less fast will it dissolve in the same amount of water.
Since at 50 C it takes 1 minute to dissolve, at 20 C which is lower temperature it will take more time to dissolve.
Answer 2
Transition metals
Explanation:-
Hardness depends on the extent of metallic bonding for metals. More the number of electrons more the metallic bonding.
Alkali metals with just 1 valence electron have weak metallic bonding. Alkaline earth metals have just 2 valence electrons. Transition elements has more electrons in penultimate shell and valence shell than lanthanides. Transition metals with most metallic bonding are the hardest
Answer:
I think b is the correct answer
