Video Transcript
Steel, a solid solution consisting
of carbon atoms seated in the holes of an iron atom structure, is an example of
blank. (A) An alkali metal, (B) a pure
metal, (C) a substitutional alloy, (D) an interstitial alloy.
This question seems to describe a
structure like this. There are iron atoms that form a
lattice structure and carbon atoms seated in the holes of the lattice. Steel is not an example of an
alkali metal. The alkali metals are the elements
in group one of the periodic table. Neither iron or carbon is found in
group one. Steel is not a pure metal, as it’s
not made of pure iron metal. So we’re left with answer choices
(C) and (D), which are both types of alloys.
An alloy is a metallic solid
solution that contains at least two different types of elements. One is a metal and the other can be
a metal or nonmetal. This question describes steel as a
solid solution, so steel is an alloy of iron and carbon. But is steel a substitutional alloy
or an interstitial alloy?
In a substitutional alloy, the
alloying element has a similar diameter to the metal atoms. The alloying element takes the
place of some of the metal atoms in the lattice. In an interstitial alloy, atoms of
the alloying element have a diameter that is significantly smaller than the metal
atoms. Atoms of the alloying element
occupy the cavity positions in the metal atom lattice.
The diagram for steel matches the
diagram for an interstitial alloy, not a substitutional alloy. It makes sense that steel would be
an interstitial alloy as the diameter of carbon atoms are significantly smaller than
the diameter of iron atoms.
So steel, a solid solution
consisting of carbon atoms seated in the holes of an iron atom structure, is an
example of an interstitial alloy, answer choice (D).
