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Module 1: Electrones

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Clasificación periódica y configuración electrónica

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XSIQ
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Chemistry - Electron configuration and periodic classification

Electron configuration and periodic classification

The modern periodic table has four distinct blocks, the s, p, d and f
blocks. Elements are located in these blocks according to the highest
energy (outermost) subshell that contains electrons.

All elements have their outermost (highest energy) electrons in an
s-subshell.

All elements have their outermost (highest energy) electrons in a
p-subshell.

All elements have their outermost (highest energy) electrons in a
d-subshell.

All elements have their outermost (highest energy) electrons in an
f-subshell.

Elements in the s- and p-blocks are also classified in vertical groups.
All elements belong to a horizontal period.

The (in Roman numerals) of an element is defined as 'the total number of
electrons present in the outermost (highest energy) shell that contains
electrons'.

The of an element is defined as 'the number of the outermost (highest
energy) shell that contains electrons' or 'the total number of shells
containing electrons'.

Magnesium (12Mg) has the electron arrangement 1s2s2p3s.

It is located in:

* period 3, because there are three shells containing electrons

* group II, because there are two electrons in the outermost shell (the
third shell)

* the s-block, because the last subshell to contain electrons is an
s-subshell

Iron (26Fe) electron arrangement 1s2s2p3s3p4s3d / 1s2s2p3s3p3d4s

It is located in:

* period 4, because there are four shells containing electrons

* the d-block, because the highest energy subshell is the 3d subshell

At one time considered part of group VIII, iron is now usually classified
as a transition element.

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