In the Lewis dot diagram for elements there is no special orientation for the dots.  The only stipulation is that unpaired electrons are shown  as such. For instance, oxygen has the ground state valence electron configuration, 2s²2p⁴  Two of the p electrons are unpaired, therefore they should be displayed as single dots.

 

 

When the oxygen picks up 2 electrons to form oxide ion, O ^2-, the unpaired electrons are now paired. 

 

Returning to the KCl example. In order for K to obtain a noble gas configuration, it can either lose a single electron becoming isoelectronic with argon or gain 7 electrons to gain the electron configuration of krypton.

 

  

Based on your chemical knowledge, which process do you think is more likely to occur?  Lose 1 e- or gain 7 e-?  Consider the charge on the resulting ion in each case.

 

In the reaction of K with Cl it is energetically more favorable for K to lose one electron. Likewise Cl gains K's lost electron, and together they give the Lewis dot diagram for KCl. When showing ionic compounds the charge on the ions is included in the Lewis dot representation.

 

Let us look at another ionic compound, CaBr₂.  Notice that the Lewis diagram for Br’s valence shell is the same as that of Cl.