Video Transcript
Nitrogen ordinarily has seven
protons and seven neutrons. Which figure describes the
electronic configuration of a single nitrogen atom?
The question mentions the element
nitrogen. Nitrogen has the symbol capital
N. We are told that nitrogen has seven
protons. Protons are found in the nucleus of
an atom. Protons are positively charged
particles. We are also told that nitrogen
usually has seven neutrons. Neutrons are also found in the
nucleus of an atom. Neutrons are neutral particles. In other words, they are not
charged. Let’s remove the answer options for
now. We need some space to draw what we
know to figure out the answer to this question.
In the picture, we can see the
nucleus of an atom, which contains protons and neutrons. The number of protons depends on
the element. Another type of particle in atoms,
electrons, are found outside the nucleus. Electrons are negatively charged
particles. In any atom, the number of protons
equals the number of electrons. This is because atoms are
electrically neutral overall. They have no overall charge. They have the same number of
positively charged protons as negatively charged electrons. So, all the charges cancel out.
We are asked to select the figure
which shows the electronic configuration of a nitrogen atom. So, what does electronic
configuration mean? Electronic configuration is the
distribution of electrons in energy levels. In other words, electronic
configuration is the way the electrons are arranged into energy levels in an
atom. The first energy level, energy
level K, can hold a maximum of two electrons. The second energy level, energy
level L, can hold a maximum of eight electrons. The second energy level only gets
electrons when the first energy level is full. And the third energy level, energy
level M, can hold a maximum of 18 electrons. I haven’t drawn them all in. This third energy level only gets
electrons when the second energy level is full.
Knowing this, we can now figure out
the electronic configuration of a nitrogen atom. Since a nitrogen atom is neutral
overall and since it has seven protons in its nucleus, we can deduce that it has
seven electrons. The seven electrons of a nitrogen
atom begin to fill the first energy level, energy level K, first. This energy level gets two of the
seven electrons. Now five electrons remain. These five electrons go into the
second energy level, energy level L. All seven electrons of the nitrogen
atom are in energy levels. Note that the second energy level
is not full. It can hold up to eight
electrons. Also, the third energy level,
energy level M, contains no electrons.
Now it’s time to bring back the
answers. We can see that the figure which
matches the one we drew is figure (C), with two electrons in energy level K and five
electrons in energy level L. Finally, which figure describes the
electronic configuration of a single nitrogen atom? The answer is figure (C).
