Video Transcript
Which of the following is not an element? (A) Uranium, (B) molybdenum, (C) carbon, (D) steel, or (E) iron.
Let’s start by reviewing the definition of an element. An element is a type of atom with the same number of protons. The elements are listed on the periodic table of the elements. Each entry on the periodic table corresponds to a uniquely named element with a certain number of protons. If we can find the name on the periodic table of the elements, that means it’s an element. If we find the sixth element of the periodic table, the six corresponding to the six protons in the nucleus of atoms of that type, we find carbon. Carbon is indeed an element since it’s on the periodic table. So we can cross it off our list as we’re looking for something that is not an element.
Let’s see what other elements we can find on the periodic table. Uranium, element number 92, can be found among the lanthanides and actinides in the separated portion of the periodic table toward the bottom. These two rows of the periodic table could be inserted to join the rest of the periodic table above. However, they’re removed to prevent the periodic table from becoming too wide and to provide easier visibility. Molybdenum, shortened with the chemical symbol Mo and with the atomic number 45, can be found in the center left of the periodic table. Since molybdenum is on the periodic table of the elements, we know that it is an element and is not the correct answer.
Next, iron, with the chemical symbol Fe and an atomic number of 26, can be found in the upper center of the periodic table. Note that the chemical symbols of most of the elements, including uranium, molybdenum, and carbon, include the first or first two letters of the name. However, for iron, its chemical symbol is completely different. Why is this? The chemical symbol for iron, Fe, is derived from its Latin name, ferrum. The other elements with atypical chemical symbols include some well-known metals, such as gold, silver, copper, tin, and lead.
When searching the periodic table for a specific element, keep in mind that the chemical symbol may or may not include the first or first two letters of that element’s name. We’ve located uranium, molybdenum, carbon, and iron on the periodic table, but steel is nowhere to be found. Thus, we know that steel is the correct answer. It is not an element, as it’s not on the periodic table.
But if steel is not an element, what is it? Steel is a type of material called an alloy, which is a metal made by combining a metal with other elements. If we could zoom in to see the atoms that make up steel, it would look something like this, with the smaller carbon atoms packed in between the larger iron atoms. Steel is a common component of structures and machines, in part because this tightly packed structure of atoms gives it additional strength. And it’s relatively cheap to produce. Based on this structure, we know that steel is not an element. Instead, it is composed of multiple different elements added together. So our final answer is that (D) steel is not an element.
