To convert the expanded form into exponent form or what is commonly known as scientific notation, you have to move the decimal place until you reach the last digit. From its original place, there are 6 places in order to reach to the last digit. Since you moved to the right, the exponent would have a positive sign. The scientific notation would be 6×10⁶ m.
Atomic mass Kr = 83.8 g/mole
Atomic mass Ar = 39.948 g/mole
So the ratio of the effusion rates = SQRT(83.8/39.948) = 1.45. Argon moves 45% faster than krypton!
Hope that helped!
When looking down the groups the elements have an equal number of electrons in the outer shell. This means they react in a similar way making it easier for scientists to use.