Answer:
i think it is the last option a pure substance that can be separated into different elements by chemical means
Explanation:
I believe it’s the last option
207 is the mass number. 82 would be the atomic number
Answer: The given statement is true.
Explanation:
According to the Dalton's law, total pressure of a mixture of gases that do not react with each other is equal to the partial pressure exerted by each gas.
The relationship is as follows.

or, 
where,
....... = partial pressure of individual gases present in the mixture
Also, relation between partial pressure and mole fraction is as follows.

where,
= mole fraction
Thus, we can conclude that the statement Dalton's law of partial pressures states that the total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture, is true.
The oceanic part of the earth is the liquid portion Of the planet