Mass Number Chemistry Example 5

Follow the full solution, then compare it with the other examples linked below.

Example 5

easy
An atom has 17 protons and 18 neutrons. What is its mass number?

Solution

  1. 1
    Mass number is the total of protons and neutrons.
  2. 2
    So the mass number is 17 + 18 = 35.

Answer

35
Mass number counts the particles in the nucleus: protons plus neutrons. Electrons are not included because their mass is negligible and they are outside the nucleus.

About Mass Number

The total count of protons and neutrons (collectively called nucleons) in an atom's nucleus, always a whole number, used to identify specific isotopes of an.

Learn more about Mass Number →

More Mass Number Examples

Example 1 easy

An atom has 17 protons and 18 neutrons. What is its mass number and what element is it?

Example 2 medium

Why is the atomic mass of chlorine listed as [formula] amu on the periodic table, rather than a whol

Example 3 medium

An isotope has 26 protons and 30 neutrons. What is its mass number? Identify the element.

Example 4 easy

Find the mass number of an atom with 26 protons and 30 neutrons.

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