What structural feature is different in isotopes of a particular element?

The term atomic structure describes the arrangement of particles within an atom. At the heart of an atom lies its nucleus, a dense core consisting chiefly of protons and neutrons. Protons are positively charged particles, and their number in the nucleus (atomic number) defines the identity of the chemical element. For example, all carbon atoms have 6 protons. Electrons, with their negative charge, orbit the nucleus in various energy levels, creating a balance with the positive charge of the protons.

Electrons are significant in chemical interactions, but they have a much smaller mass compared to protons and neutrons and therefore don't contribute much to an atom's mass. Understanding atomic structure is fundamental when studying chemistry, as it provides essential insights into the behavior of elements and how they combine to form compounds.

Isotopes are variations of a chemical element that have the same number of protons but different numbers of neutrons. The presence or absence of neutrons alters the mass of the isotopes without changing the chemical properties. For instance, carbon-12 and carbon-14 are isotopes of carbon; both have 6 protons, but carbon-12 has 6 neutrons whereas carbon-14 has 8 neutrons.

The difference in the number of neutrons can result in isotopes having different stability. Some isotopes are stable, while others are radioactive and can decay over time, emitting radiation. This property of radioisotopes has practical applications in fields such as medicine, where they are used for both diagnosis and treatment.

The atomic number of an element is the number of protons found in the nucleus of one of its atoms. It is a distinctive property that defines the element and is represented by the symbol Z. On the other hand, atomic weight, also known as relative atomic mass, takes into account the average mass of the mixture of its isotopes as they occur naturally. Represented by the symbol A, it depends not only on the number of protons but also on the number of neutrons in the nucleus.

Since the atomic number is fixed for any given element but neutrons can vary, isotopes of the same element have the same atomic number but different atomic weights. The atomic weight is important, especially in chemical calculations and when determining the ratios of elements in compounds.