The symbol of an isotope is:

A - the mass number
Z - the atomic number
X - the symbol of an element
The symbol of oxygen is O.
The atomic number is the same for all isotopes of one element. For oxygen it's 8, because every atom of oxygen has 8 protons in its nucleus.
The mass number is the number of nucleons (protons + neutrons) in the nucleus of an atom, and it's given in the name of an isotope. Oxygen-16 has the mass number 16, oxygen-17 has the mass number 17, oxygen-18 has the mass number 18.
Oxygen-16:

Oxygen-17:

Oxygen-18:
Answer:
The heat gain by the system,
q
=
−
250
kJ
.
The work done on the system ,
w
=
−
500
kJ
.
The First Law of Thermodynamics state that
Δ
U
=
q
+
w
=
−
750
kJ
Explanation:
Answer:
A substance made of two or more atoms bonded together is a compound.
I think...
Under normal circumstances, it's an "S" shape. The graph below shows both a normal Bhor diagram and one during exercise or what otherwise would cause a high release of Carbon dioxide. Oxygen dissociates much more readily and easily if the concentration of CO2 is higher.