no u dont ned any.
It is not really wrong to use periods when abbreviating South Carolina S.C.; in fact, most folks over 50 can remember when it was preferred. But today adding the periods is considered old style. The US Postal Service (USPS) abbreviation for each of the United States, districts, territories, and possessions dispensed with the periods.
Yes P.E. it's an abbreviation. But check the style manual that you are to use for your writing. Most schools and corporations have one designated, or have created their own, that specifies the correct method for abbreviations.
4 periods are used when an omission ends a sentence.
That string of periods is called an ellipsis. Ellipses take the place of text that has been omitted from the sentence.
No
Never. When ending a sentence with an abbreviation, a single period will suffice. It does double duty in finishing the abbreviation and the sentence. You may, however, see three periods at the end of a sentence. This is an ellipses. Or, two periods may occur in a sentence that includes a quote. Example: When I heard him say, "I found your luggage.", I cried tears of joy.
at the end of a sentence
They are used to mark the end of a sentence.
Ellipsis . . .
there are 5 minutes in between periods.
To answer your question. You will have to put TWO periods.
Periods end a sentence. They are punctuation marks that look like dots.