Chemistry Scientific Notation

23 X 10^5 is not in proper scientific notation. Why?

In the United States, 15,000,000 households use private wells for their water supply. Write this number in scientific notation.

The U.S. has a total of 1.2916 X 10^7 acres of land reserved for state parks. Write this in standard form.

Using Scientific Notation, rewrite the following number: 0.000882

Using Scientific Notation, rewrite the following number: 8.82 x 10^-4

Using Scientific Notation, rewrite the following number: 0.00000059

Using Scientific Notation, rewrite the following number: 5.9 x 10^-7

Using Scientific Notation, rewrite the following number: 0.00004

Using Scientific Notation, rewrite the following number: 4 x 10^-5

The nucleus of a human cell is about 7 X 10^-6 meters in diameter. What is the length in standard notation?