One billion in scientific notation is expressed as 1 x 109.
Scientific notation is a way to write very large or very small numbers in a compact form. It consists of two parts: a number between 1 and 10, and a power of ten. In the case of one billion, we start with the number 1, which we then multiply by 10 raised to the power of 9. This reflects that one billion is equal to 1 followed by 9 zeros (1,000,000,000).