Atoms are the fundamental building blocks of matter and an element is a pure substance that consists of only one type of atom. Atoms are connected to an element by the number of protons in their nucleus. The number of protons in the nucleus determines the element's atomic number, which is unique for each element and is used to identify it.

All atoms of an element have the same atomic number, but they may have different numbers of neutrons, resulting in different isotopes of the element. Isotopes have the same number of protons and electrons, but different numbers of neutrons.

The properties of an element are determined by the number and arrangement of its electrons. Electrons are negatively charged subatomic particles that orbit the nucleus of an atom. The number of electrons in an atom is equal to the number of protons, so atoms are electrically neutral. Electrons are arranged in shells around the nucleus, and the outermost shell determines the atom's chemical properties.

Atoms of the same element have the same number of electrons and the same electron configuration, which means that they behave similarly in chemical reactions. This is why elements are grouped together in the periodic table, which is a chart that organizes elements based on their atomic numbers, electron configurations, and chemical properties.