Video Transcript
Which of the following statements
explains why metals generally have high densities? (A) They are poor conductors of
thermal energy. (B) They can be drawn out into a
wire without breaking. (C) They can be bent or hammered
into certain shapes without shattering. (D) They shatter when bent or
hammered. Or (E) they have a closely packed
crystalline lattice.
Let’s start by looking at what we
mean by high density. A high density means that a
substance has a high mass for the size or volume that the substance takes up. Metals have a high density because
they have many atoms packed very closely into a small space. This is primarily due to metallic
bonding.
Metallic bonding is the strong
electrostatic attraction between metal cations and delocalized electrons. This results in a regular
arrangement of a crystalline lattice structure. In between the metal cations, the
delocalized electrons can flow throughout the lattice. It is this specific structure that
leads to some of the distinctive properties of metals.
Answer choices (B) and (C) discuss
some of these properties. For example, metals can be drawn
out into a wire without breaking, a useful property called ductility. Answer choice (C) discusses metals’
ability to be bent or hammered into different shapes, another useful property called
malleability. However, these statements do not
explain why metals have a high density. We can eliminate answer choices (B)
and (C).
Because of the ease with which
electrons can move through the lattice, metals are good conductors of thermal
energy. Answer choice (A) does not describe
metals at all, so we can eliminate it. Answer choice (D) suggests that
metals do shatter when manipulated, which would be a property called
brittleness. Metals are not brittle, so we can
eliminate answer choice (D).
Answer choice (E) talks about the
arrangement of metal atoms in a similar fashion to what we have already
discussed. It is this unique lattice
arrangement in metals that give them the property of high density.
Therefore, the statement that
explains why metals generally have high densities is answer choice (E). They have a closely packed
crystalline lattice.
