Answer: 1.67x10^-21
Explanation: The number 1.67E−21 is already in scientific notation. Scientific notation is a way of expressing very large or very small numbers in a compact form using powers of 10.
In this case, 1.67E−21 means 1.67 multiplied by 10 raised to the power of -21.
To understand this notation better, let's break it down:
1. The number before "E" (1.67) is the coefficient. It is always a number between 1 and 10.
2. The "E" represents the exponent.
3. The number after "E" (-21) is the exponent or power of 10. It indicates how many times you need to multiply the coefficient by 10.
So, in scientific notation, 1.67E−21 represents the mass of 1,000 protons in grams, where the mass is 1.67 multiplied by 10 raised to the power of -21 grams.