How do you find the mass number of a single Atom

Subject : Chemistry

Question:

How do you find the mass number of a single atom, when the atomic mass is known?

Expert Verified Solution:

Description: Finding the mass number of a single atom involves understanding the relationship between atomic mass and the individual particles in the atom. The mass number is a whole number representing the sum of protons and neutrons in the nucleus. Although atomic mass (which accounts for the presence of isotopes and their relative abundance) can be a decimal, the mass number will always be an integer.

To find the mass number of a single atom when the atomic mass is known:

1. Round the Atomic Mass: Start by rounding the atomic mass to the nearest whole number. The atomic mass is typically found on the periodic table and is the weighted average of all isotopes of that element.

2. Understanding the Concept:

• The atomic mass is generally close to the mass number of the most common isotope.
• The mass number is the sum of protons and neutrons in a single atom.

3. Example:

• Suppose the atomic mass of an element is 12.01 amu (atomic mass units).
• Round 12.01 to the nearest whole number: 12.
• This rounded number represents the mass number for the most common isotope of that element.

Final Mass Number: The mass number for this atom is 12.