Arrange these elements in order of decreasing atomic size: sulfur, chlorine, aluminum, and sodium. does your arrangement demonstrate a periodic trend or a group trend

Arranging the given  elements in order of decreasing atomic sizes ;

The arrangement of elements based on Atomic numbers is a periodic trend ( because elements are categorized/ put in different patterns  in the periodic table based on their atomic sizes ).  while

A group trend groups elements in vertical order based on their characteristics and not atomic size.

Hence we can conclude that Arranging the various elements in order of decreasing atomic sizes is ; Sodium > Aluminum > Sulfur > Chlorine

Learn more : link

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.