Questions: app.aktiv.com Question 9 of 15 What is the atomic number for an element whose mass number is 78 , which contains 38 neutrons per atom?

Solution Steps

The mass number (A) of an element is the sum of its protons (atomic number, Z) and neutrons (N). This relationship can be expressed as: \[ A = Z + N \]

We are given:

• Mass number \( A = 78 \)
• Number of neutrons \( N = 38 \)

Using the relationship \( A = Z + N \), we can solve for the atomic number \( Z \): \[ Z = A - N \] Substituting the given values: \[ Z = 78 - 38 \] \[ Z = 40 \]

Final Answer