In this question, we're asked to write the
chemical symbol of an element in period
two and group 7A of the periodic table.
And as another example, we're also going
to find Period three in group 2A. So the
periodic table is arranged in periods,
which are your horizontal rows on the
periodic table, and groups, which are your
vertical columns on the periodic table.
You may recall from the class that
elements in the same group have similar
chemical properties. So the noble gases
for example have similar chemical
properties in Group 8A or 18, and/or
halogens in group 7 or 17 have similar
chemical properties to each other.
However for this question, all we need to
know is that the periods are the
horizontal rows and the groups are the
vertical columns. So going back to the
original question, period 2, group 7A,
period 2, group 7A, it's a halogen, it's
fluorine. Also as my other example, period
3, group 2A, so period 3, 2A which is an
alkali earth metal, which is magnesium.
