Review the electron configurations of the elements in period 3, from sodium (Na) to argon (Ar). What do you observe?

Electronic configuration represents the total number of electrons that a neutral element contains. We add all the superscripts to know the number of electrons in an atom.  The electrons are filled according to Afbau's rule in order of increasing energies.

The last electron enters the third shell in all elements from Sodium to Argon.

consider the reaction below.

 no rx

at 500 k, the reaction is at equilibrium with the following concentrations.

[pci5]= 0.0095 m

[pci3] = 0.020

[ci2] = 0.020 m

what is the equilibrium constant for the given reaction?

0.042

0.42

2.4

24

what are the statements