Nobel gas, it is in the last row of the periodic table and therefore is a noble gas
Matter that has a uniform and definite composition is called a vapor
A O-18 has 2 more neutrons than O-16
<h3>Further explanation</h3>
Oxygen is located in group 16 in the p block which has the atomic number 8
In the atomic symbol (neutral), the atomic number indicates the number of electrons and protons. while the number of neutrons is obtained from the difference between the mass number and the atomic number.
The isotope will have the same number of protons (atomic number) but a different mass number
Isotopes of oxygen include: O-18 and O-16

The density of substance that contain 850 milligrams for every Ml is
0.85 g/Cm³
calculation
<em> </em><em>step 1:</em><em>convert 850 Mg to g</em>
<em>that is 1 mg=0.001 g</em>
<em> 850 mg =? g</em>
<em>= (850 mg x 0.001 g)/ 1 mg=0.85 g</em>
<em>step 2: convert Ml to Cm³</em>
<em> that is 1 Ml = 1 cm³</em>
<em>therefore density =</em><em> 0.85 g/Cm³</em>