A neutral sulfur atom has 16 protons and 16 neutrons. What is the atomic mass of this atom?
The correct answer and explanation is :
The atomic mass of a neutral sulfur atom with 16 protons and 16 neutrons is 32 atomic mass units (amu).
Explanation:
The atomic mass (or atomic weight) of an atom is the weighted average mass of the atoms in a naturally occurring sample of an element, based on the abundance of its isotopes. For an individual atom, however, the atomic mass is approximately the sum of the number of protons and neutrons in its nucleus.
- Protons are positively charged particles found in the nucleus, and the number of protons determines the atomic number of the element. In the case of sulfur (S), the atomic number is 16, meaning sulfur has 16 protons.
- Neutrons are uncharged particles also found in the nucleus. In this particular example, the sulfur atom has 16 neutrons.
To calculate the atomic mass of this specific sulfur atom, we add the number of protons and neutrons:
$$
\text{Atomic Mass} = \text{Number of Protons} + \text{Number of Neutrons} = 16 + 16 = 32 \, \text{amu}.
$$
While protons and neutrons each have a mass close to 1 amu, the mass of electrons is negligible because they are much lighter than protons and neutrons. Therefore, the atomic mass of this neutral sulfur atom is approximately 32 amu.
This sulfur atom has an atomic mass of 32 amu, which corresponds to the most common isotope of sulfur, known as sulfur-32 (S-32). This isotope of sulfur is stable and makes up approximately 95% of the sulfur found in nature. Other isotopes of sulfur, such as sulfur-33, sulfur-34, and sulfur-36, exist, but they are much less abundant and have different numbers of neutrons. The atomic mass of an element in the periodic table is typically a weighted average of all its naturally occurring isotopes.