It is important to know the difference between atoms, ions, and isotopes. choose all of the correct answers. an atom of oxygen and the ion of oxygen both have 8 protons. electrons must be removed from a carbon atom to form an isotope. the atomic mass of metals is calculated differently that the atomic mass of nonmetals. as you add or remove neutrons from the nucleus, isotopes are formed. the most massive subatomic particles are electrons. the isotope of carbon and the atom of nitrogen both have 7 protons in the nucleus.

Answer : The correct options are,

An atom of oxygen and the ion of oxygen both have 8 protons.

As you add or remove neutrons from the nucleus, isotopes are formed.

Explanation :

Isotope : Isotope is the chemical element in which the number of protons and electrons are same but differ in the number of neutrons. And the atomic mass also different. The atomic number is always same.

This statement is correct because there is no change in the number of protons only changes in the number of electrons.

This statement is incorrect because when we remove electrons, the atomic number changed. By changing the atomic number, the element will also changed.

this statement is incorrect because there is no different method used for the calculation of the metal and non-metal.

This statement is correct. Isotope is the chemical element in which the number of protons and electrons are same but differ in the number of neutrons. And the atomic mass also different. The atomic number is always same.

This statement is incorrect because electrons are the lighter subatomic particle as compared to the protons and the neutrons.

This statement is incorrect because in the isotope of carbon, the number of neutrons are different but the number of protons are always be 6. The number of protons in the nitrogen atom is 7.

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation:

if you mean hydrogen and oxygen then water is the product