Which statement best describes the nature of most new elements added to the periodic table in the last hundred years?

• A. They are synthetic elements created in laboratories and are typically unstable.
• B. They are stable elements found in large quantities in nature.
• C. They are noble gases with high chemical inertness.
• D. They are naturally occurring elements discovered in Earth's crust.

Answer: (A)

Verified step by step guidance

1. Understand that the periodic table has expanded significantly in the last hundred years primarily due to the discovery and creation of new elements beyond those naturally found on Earth.
2. Recognize that many of these new elements are not found in nature but are synthesized artificially in laboratories through nuclear reactions, often involving particle accelerators or nuclear reactors.
3. Note that these synthetic elements typically have very high atomic numbers and are often unstable, meaning they have short half-lives and decay quickly into other elements.
4. Contrast this with naturally occurring elements, which are generally stable or have long half-lives and are found in the Earth's crust or atmosphere.
5. Conclude that the best description of most new elements added recently is that they are synthetic, created in labs, and usually unstable, rather than being stable, naturally occurring, or noble gases.