Answer: 16 neutrons
Explanation: The atomic number for any element is the number of protons in its atomic nuclei. In a neutral atom, the number of electrons are the same as the number of protons. The atomic mass (mass number) is the sum of the protons and neutrons in the nucleus. Mass number can vary due to the fact that the number of neutrons can vary. Isotopes are named for their mass numbers.
So, this element has 15 protons (atomic number), 15 electrons, and 16 neutrons (mass number minus atomic number).
This isotope is phosphorus-31, which has atomic number 15.
We are given with a <span>temperature of 273.15 Kelvin and a pressure of 101.325 kPa. Using PV=nRT rule of ideal gas, where P is pressure, V is volume, n is the number of moles, R is the gas constant and T is temperature, we can conclude that the conditions are under STP(standard temp and pressure) and one mole of this gas occupies 22.4 L of volume.</span>
I think answer youre looking for is 2Na+O->Na2O . But sadly it is wrong since we dont use atomic oxygen in reactions. It should be rather
4Na+O2 => 2Na2O but it doesnt correspond to ratios given.