Question

atomic mass is a average of all isotopes of an element.

Explanation:

Atomic mass is calculated based on the relative abundances of an element's isotopes. It's a weighted average, where each isotope's mass is multiplied by its abundance (as a decimal), and then these products are summed. For example, if an element has two isotopes: isotope A with mass \(m_A\) and abundance \(x_A\), and isotope B with mass \(m_B\) and abundance \(x_B\) (\(x_A + x_B=1\)), the atomic mass \(M = m_Ax_A + m_Bx_B\). This method accounts for the fact that different isotopes contribute differently to the overall atomic mass according to how common they are.

Answer:

weighted