C.
Anthracite has the highest carbon compact and fewest impurities.
Also, the highest calorific of all types of coal except for graphite.
Answer:
The atomic radius corresponds to Sigma
Explanation:
It is the Van Der Waals radius ;)
In the lake that the rivers lead, water molecules evaporate into the sky and form clouds. In the sky, these water droplets condense and form clouds that will eventually rain.
Characteristics of a Precipitate:
A precipitate is characterized by the following properties:
Appears as a solid species.
Settled down at the bottom of the reaction pot.
Insoluble in the corresponding solvent.
Let's eliminate these one by one.
The first pair would not be the same, as X would most likely be in group IA, and Y would be in group VIIA, because of their tendency to gain and lose electrons.
The second pair would also violate the same rule, but X would most likely be in group IIA, and Y would most likely be in group VIA.
The third pair would not be the same, as X is most likely in group VIIA, and since Y has eight valence electrons, it is most likely a noble gas.
The final pair has X with atomic number 15, making it phosphorous. Phosphorous wants to gain 3 electrons to have a full octet of 8 outer "valence" electrons, and Y would also like to gain 3 electrons. This means it is possible that the final pair would be in the same group.
