Video Transcript
Which letter corresponds to the elements in the periodic table that are the most electronegative?
This question is about electronegativity. Electronegativity is defined as the tendency of an atom to attract a bonding pair of electrons. For example, the covalent bonds that hold together a water molecule represent a pair of shared electrons. Since the oxygen atom is more electronegative than the hydrogen atoms, it has a stronger attraction to the bonding pairs of electrons. As a result, those electrons pull in closer to the oxygen atom than to the hydrogen atoms.
This question is asking us to look at the periodic table and find the trends in electronegativity. In other words, how does electronegativity change as we move side to side or up and down on the periodic table? If we can understand these two directional trends, we can find the corner of the periodic table that is likely to have the highest electronegativity values.
Let’s start analyzing the horizontal trend by looking at two elements that are on opposite ends of the same period. One significant difference between potassium and bromine is the number of valence electrons. Potassium with just one valence electron has a nearly empty outermost electron shell. Meanwhile, bromine with seven valence electrons has a nearly full outer electron shell. Potassium with its one valence electron is more likely to give up that electron and is unlikely to gain or attract electrons.
On the other hand, bromine is just one electron away from filling that outer electron shell. So it is much more likely to gain electrons or attract them. From this comparison, we can describe the horizontal trend for electronegativity on the periodic table. Electronegativity increases as we move from left to right across a period.
To investigate the vertical trend in electronegativity, let’s take a look at two elements that are in the same group but different periods. Fluorine and bromine are both halogens. However, fluorine has nine electrons split between two electron shells, whereas bromine has 35 electrons that occupy four electron shells. In this diagram, we can clearly see that fluorine has a smaller atomic radius than bromine. A smaller atom means that its nucleus is closer to the bonding electrons that the atom interacts with. As a result, there’s a stronger attraction between the nucleus and those electrons. In other words, there’s a higher electronegativity.
The opposite is true for bromine; it has a larger atomic radius. Its nucleus is farther from the bonding electrons, so there is a weaker attraction and a lower electronegativity value. From this comparison, we can describe the vertical trend in electronegativity on the periodic table. Electronegativity increases as we move from the bottom to the top of a group.
With the two trends explained, we can select the letter that represents the portion of the periodic table with the most electronegative elements. Combining the two trends, we can say that the top right of the periodic table will have the most electronegative elements. These are the elements with nearly full electron shells and small atomic radii. To answer this question, we can write the letter B, the correct answer. So, which letter corresponds to the elements in the periodic table that are the most electronegative? That’s the letter B in the top right of the periodic table.
