Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Problem:Passage: The smallest particle of an element that still has the properties of that element is the atom . Atoms actually consist of smaller particles, including protons and electrons, but these smaller particles are the same for all elements. All the atoms of an element are like one another, and are different from the atoms of all other elements. For example, the atoms of each element have a unique number of protons. Answer: atom
Solution:
What is the smallest part of an element called?