Describe the relationship between an element's row number in the periodic table and the highest

Describe the relationship between an element's row number in...

Key Concepts

Transition Element Electron Configurations

Transition metals exhibit a more complex relationship because they begin filling (n-1)d orbitals even as the new, higher n level is being occupied by s electrons. Although the period number indicates the highest n, the involvement of lower-energy (n-1)d electrons means that the correlation is not as direct as in main-group elements.

Main-Group Element Electron Configurations

For main-group elements, the relation is straightforward: the period number is equal to the highest principal quantum number observed in the element’s electron configuration. This direct correlation arises because the electrons in these elements are added to a new shell that mirrors the period number.

Inner Transition Element Electron Configurations

Inner transition elements (the lanthanides and actinides) involve the filling of f orbitals, which belong to an inner shell (with a principal quantum number two less than the period number). This results in a disparity where the highest principal quantum number of the valence electrons (reflected by the period) does not directly match the quantum number of the electrons filling the f orbitals.

Principal Quantum Number

This quantum number (n) represents the main energy level of an electron in an atom. It not only determines the electron’s average distance from the nucleus but also reflects the general energy and size of the orbital. The highest principal quantum number in an element’s electron configuration indicates the outermost energy level that contains electrons.

Periodic Table Rows (Periods)

Each row in the periodic table, known as a period, signifies the sequential filling of electron shells in atoms. The period number for main-group elements directly corresponds to the highest principal quantum number, as each new row introduces electrons into a new, higher energy level.

Transcript

00:01 So by now, hopefully you all are familiar with assigning an element to its highest energy sub -level and its principal quantum number.

00:09 So, for example, for oxygen, you know that's in the second row right here, and you know that's in the p region right here.

00:16 So therefore, its highest energy sub -shell is 2p.

00:20 So hopefully that makes sense.

00:23 And the naming convention is pretty similar between s and p.

00:27 Right so the principal quantum number is the exact same as the row number so for example if you were to look at an element right here the principal quantum number is four because it's in the fourth row so that stays simple and it's just like that for s and p however things are different when you're dealing with the d sub level right so for the d sub level to find the principal quantum number you actually take the row total or the row number not the row total excuse me the row number and then you subtract one.

01:04 So for example, let's just say we're dealing with chromium, right? your first instinct would say that chromium is in the 4d sub -level, right? because it's in the fourth row and it's in the d region of the periodic table.

01:18 However, it's actually in the 3d subpo.

01:23 Because you have to follow this rule that it's row number minus 1.

01:28 So same thing with cobol.

01:30 Cobol is in the 3d sub -level, right? zirconium is in the 40 sub -level, so on, so forth.

01:41 Zirconium's in the fifth row, but you subtract once in the 40.

01:45 So the f block also doesn't follow regular conventions seen by s &p.

01:52 The f block is row total, or row number, i don't know why i keep saying row total...

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