Video Transcript
The diagram shows electrons in
different electron shells in an atom. The atom is electrically
neutral. What element is this an atom
of?
Okay, so in this question, we’ve
been given a diagram, which shows what appears to be the nucleus at the centre of
the atom as well as the electronic energy levels, which are represented in
black. Now, these electronic energy levels
are also known as shells. And we can see that occupying these
shells there are one, two, three blue dots representing electrons. In other words, there’re three
electrons in this atom.
Now, we’ve been told that this atom
in question is electrically neutral. This means that the overall
electric charge on the atom is zero, because it’s neutral. Now, to understand the significance
of this, we should recall that electrons are negatively charged particles. And that atoms are neutral if the
number of electrons in the atom is equal to the number of positively charged protons
found in the nucleus. And so what this diagram is telling
us is that there are three electrons in this atom. And in order for it to be neutral,
there must be three protons in the nucleus of the atom. And then, we can recall that an
element is defined by the number of protons found in the nucleus of an atom of that
element.
And so in order to find the answer
to our question, we will need to look on the periodic table. Specifically, we can recall that
the periodic table of the elements shows all of the elements arranged in order of
atomic number, where the atomic number of an atom is simply the number of protons
found in the nucleus of that atom. And so considering the periodic
table is arranged in order of increasing atomic number, we want to find the element
in the periodic table, which has an atomic number of three. Because there are three protons in
this particular atom’s nucleus. So the element that has three
protons in its nucleus is lithium. And hence, that is the answer to
our question.
