$size: xs sm md lg xlg auto;
$i: 0;

@each $col in 0.5rem, 0.85rem, 1rem, 2.2rem, 4.2rem, auto{
  $i: $i + 1;

  .pt-#{nth($size, $i)} {
    padding-top: $col;
  }
  .pb-#{nth($size, $i)} {
    padding-bottom: $col;
  }
  .pl-#{nth($size, $i)} {
    padding-left: $col;
  }
  .pr-#{nth($size, $i)} {
    padding-right: $col;
  }
}