Which of the following elements is synthetic?

uranium
iodine
helium
nobelium

No.

nobelium

To determine which of the following elements is synthetic, we need to understand what a synthetic element is. Synthetic elements, also known as man-made elements, are elements that do not occur naturally on Earth and are created through artificial means, typically in a laboratory setting.

Uranium, iodine, and helium are naturally occurring elements. Uranium is a radioactive metal that is commonly found in the Earth's crust. Iodine is a nonmetal that is commonly found in seawater and in some minerals. Helium is a gas that is the second lightest and second most abundant element in the universe.

On the other hand, nobelium is a synthetic element. It is a transuranium element that was first synthesized in 1957 by researchers at the Lawrence Berkeley National Laboratory in California through the bombardment of curium atoms with carbon ions.

In summary, the synthetic element among the options given is nobelium.