Question Video: Determining the Electronic Configuration of an Element given the Location on the Periodic Table Science

Using the periodic table, what is the electronic configuration of element X?


Video Transcript

Using the periodic table below, what is the electronic configuration of element X? (A) 3,15. (B) 2,8,5. (C) 8,8,5. (D) 2,8,8,5. (E) 1,1,2,6,2,3.

There are trends in the electronic configuration of elements across the rows and columns of the periodic table. The rows, which are also called periods, tell us the number of energy levels that are occupied by electrons. Element X is in the third row of the periodic table, so we know electrons occupy three energy levels.

With this information, we can eliminate some of our answer choices. The electronic configuration of answer choice (A) has two occupied energy levels. So we can eliminate this answer choice. The electronic configurations in answer choices (D) and (E) have four and six occupied energy levels, respectively. So we can eliminate these answer choices as well.

The columns in the periodic table, which are also called groups, tell us the number of outer electrons that atoms of an element have. These numbers show the number of outer electrons for the main group elements in the periodic table. The number of outer electrons increases as we move across the table from left to right. So element X has five outer electrons. The electronic configurations in both of the remaining answer choices have five outer electrons. So which one is the right answer? The only difference between them is the number of electrons in the first energy level.

To determine which is the right answer, we need to know that the first energy level can only contain a maximum of two electrons. That makes answer choice (B) the correct answer. So, the electronic configuration of element X is 2,8,5.

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