An element has the atomic mass 178. what does this tell us about the atom?

a. we know the protons + neutrons adds to 178, but don't know the identity of the element.

b. we know the number of protons and neutrons, so we know the identity of the element (halfnium).

c. we know the number of protons but it could have a few different numbers of protons, or isotopes.

The answer is B

Explanation:

The atomic mass () is the average mass of all the isotopes an element has, therefore it is unique, an in this case the element will be Halfnium, as the number is 178.

The atomic mass however, does not relate to the number of protons and neutrons directly, given that the atomic mass takes all the isotopes into account.

The mass number (A) on the other hand, does consider the number of protons and neutrons. The definition of mass number is A=N° neutrons+N° protons.

Let us consider the Hydrogen as an example. Hydrogen has three isotopes:

which abundance is 99.98%

which abundance is 0.02%

(traces)

In this case, the mass number for each one of the isotopes, will be 1, 2 and 3 respectively. However, the atomic mass will be the average mass of the three isotopes, therefore:

answer: ice crystals in air

the water from the water body or another source of water gets evaporated as water vapor as an effect of heat on water. these water vapor rises in the upper layers of the earth atmosphere under high atmospheric pressure. the atmospheric pressure of these water molecules starts to decrease due to the effect of cold air. the invisible water vapor condenses into visible water droplets and ice crystals.these ice crystals and water droplets being less denser than the surrounding air floats on air as clouds.