Video Transcript
Which of the following comparisons of silicon is not correct? (A) Silicon is less electronegative than carbon. (B) Silicon is more electronegative than cesium. (C) Silicon is more electronegative than oxygen. (D) Silicon is more electronegative than sodium. Or (E) silicon is less electronegative than chlorine.
We can see that all of the answer choices have something to do with how electronegative silicon is in comparison to another element. How electronegative an atom is depends on its electronegativity. Electronegativity is the tendency of an atom to attract the shared electrons of a bond.
Let’s consider two atoms that share a pair of electrons in a single covalent bond. If the pink atom was more electronegative than the orange atom, then the pink atom would attract the pair of electrons more strongly than the orange atom. And the electron density would shift towards the pink atom. The electronegativity of most atoms can be quantified using the Pauling electronegativity scale. This is a unitless scale that ranges from zero to four, with four being the most electronegative.
So, to compare the electronegativity of silicon to the other elements listed in the question, we could simply look up their Pauling electronegativity values. We could also use their relative positions on the periodic table. We can do this because, in general, the electronegativity of an atom tends to increase going from left to right across the periodic table as well as up a group.
With this in mind, let’s take a look at answer choice (A). Looking at the periodic table, we can see that carbon is directly above silicon in group 14. As electronegativity tends to increase up a group, carbon should be more electronegative than silicon. In other words, silicon is less electronegative than carbon. This means that answer choice (A) is a true statement. But we are looking for the statement which is not correct. This means that answer choice (A) cannot be the answer to this question.
Cesium is found in the bottom left-hand corner of the periodic table. As electronegativity tends to increase as we move up and to the right on the periodic table, silicon should be more electronegative than cesium. Therefore, answer choice (B) is a true statement and cannot be the answer to this question.
Oxygen is both further up and farther to the right on the periodic table than silicon. Therefore, oxygen should be more electronegative than silicon. This means that statement (C) is a false statement and should be the answer to this question. But just to be sure, let’s take a look at answer choices (D) and (E).
Silicon and sodium are found in the same period. But as silicon is farther to the right, it should be more electronegative than sodium. Thus, answer choice (D) is a true statement and cannot be the answer to this question.
Chlorine is also found in the same period as silicon. As chlorine is farther to the right, it should be more electronegative than silicon, or in other words silicon is less electronegative than chlorine. Therefore, answer choice (E) is a true statement and cannot be the answer to this question.
So we have confirmed that the comparison of silicon that is not correct is answer choice (C). Silicon is more electronegative than oxygen.
