Video Transcript
The image below shows a partially
complete list of the halogens. Which element is missing from the
group? (A) Helium, (B) sulfur, (C)
chlorine, (D) argon, or (E) calcium.
To answer this question, we must
identify the element that is missing. The missing element must be a
halogen. The halogens are a group of
elements on the periodic table. The halogens can be found in group
17 of the periodic table, which is sometimes also referred to as group seven A. Let’s find group 17 on the periodic
table.
Group 17 is the second to last
vertical column of elements. It is found on the right side of
the periodic table. It is a group of nonmetals. If we have a closer look, we can
see the five elements that make up the halogen group. These elements are fluorine,
chlorine, bromine, iodine, and astatine. These elements are diatomic. This means that their molecules are
composed of two atoms bonded together. This is why the chemical formulas
for the halogens are written to represent two of the atoms bonded together, as shown
in pink.
We can see that the element missing
from the list given in the question is chlorine. Chlorine is a poisonous, green
gas. It is rarely found in its elemental
form but forms many important salts. It is even a component of table
salt. In conclusion, the element missing
from the partially complete list of the halogens is chlorine, answer choice (C).
