Interpret and evaluate powers with whole-number exponents, including integer and negative bases, zero exponents, parentheses, and the product, quotient, and power-of-a-power rules, without using negative or fractional exponents. Recognize perfect squares and determine their principal square roots from 0 through 225, and estimate nonperfect square roots between consecutive integers whose squares bound them. Write large and small nonzero numbers in scientific notation and convert between scientific and standard form, using $a \times 10^n$ with $1 \le a < 10$ and interpreting positive and negative integer exponents through place value.