Answer:
is the isotopic notation of the atom
Explanation:
The isotope notation is:

<em>Where a is the mass number = Number of protons + Number of neutrons</em>
<em>b is atomic number = Number of protons</em>
The atomic number define the nature of the atom, the element with atomic number = 15 is phosphorus, P:

a = 15 protons + 16 neutrons = 31
b = 15
is the isotopic notation of the atom.
Answer: The new pressure is 3 psi.
Explanation:
Given:
= 12 psi, 
= ?, 
Formula used is as follows.

Thus, we can conclude that the new pressure is 3 psi.
Answer:
Sample C is most likely the metal.
Explanation:
The Sample C is the metal, because the properties given in the sample c are all of the metal. As we know that the metals are the lustrous or the shiny elements. They are often good conductor of heat and also electricity. The metals possess high melting point. The density of the metals are heavy for their size. Metals can be easily hammered, and hence are malleable. They can easily be stretched into wires hence are ductile. They remains solid at room temperature but in case of mercury it remains as liquid. Metals are opaque object and cannot be see through it.