Question

What's the nucleon number of oxygen?

Answer 1

Mass is both a property of a human body and a measure of its resistance to acceleration when a net force is applied. An object's mass also determines the strength of its gravity to other bodies. The SI base unit of mass is the kilogram.

Complete answer:
The nucleon number is the mass of a specific atom individually and is measured in mass Units (AMU); these will always be whole numbers. The foremost common Isotope is found by rounding the weighted average found on the table to the closest integer. The foremost common isotope Mass of Oxygen is 16 mass Units.
The Weighted Average mass for every element is found on the table (That long decimal number near the rock bottom of every box). This number could be a combination of all the known Isotopes and basically tells you the typical mass you'd expect per atom if you grabbed a random few of them.
Because protons and neutrons are roughly equal in mass, an isotope's number is adequate to the sum of its protons and neutrons. Therefore, oxygen 16 has 8 protons and eight neutrons, oxygen 17 has 8 protons and 9 neutrons, and oxygen 18 has 8 protons and 10 neutrons.

Note :
Oxygen is the element with the symbol O and number 8. It's a member of the chalcogen group within the table, a highly reactive nonmetal, and an oxidant that readily forms oxides with most elements also like other compounds.