@tomanderson well, the smallest structural element considered in chemistry is atom. Protons and neutrons are more domain of physics. Atoms may assemble directly into lattice or assemble into molecules that assembles into lattice or molecules can be included into a lattice/molecule.
What Is the Fundamental Structural Unit of an Element?
Atoms are the basic units of matter and the defining structure of elements. The term “atom“ comes from the Greek word for indivisible, because it was once thought that atoms were the smallest things in the universe and could not be divided.
The structure of an atom is a central nucleus composed of protons and neutrons with electrons orbiting around this nucleus.
All atoms of an element have the same number of protons in their nucleus. The number of protons in the nucleus determines which element an atom is.
For example, all atoms of carbon have six protons in their nucleus. The number of protons in an element‘s nucleus is also called the element‘s atomic number.
The number of neutrons in an element‘s nucleus can vary. Atoms of the same element with different numbers of neutrons are called isotopes.
Most atoms have an equal number of protons and neutrons. For example, most carbon atoms have six protons and six neutrons. The number of electrons in an atom is usually equal to the number of protons in the nucleus.
The arrangement of electrons around the nucleus is called the electron configuration. The configuration of an atom can affect the atom‘s chemical properties. The term “element