The correct option is A Proton
Mass of an electron =9.1×10−31 kg
Mass of a proton =1.67×10−27 kg
First Method–––––––––––––––––
Step 1:
Write the numbers in scientific notation. Here, the masses 9.1×10−31 kg and 1.67×10−27 kg are already in scientific notation.
Step 2:
Compare the exponents of numbers. The larger the exponent, the greater the number.
∵ −27>−31
⟹1.67×10−27>9.1×10−31
Therefore, proton has a greater mass than the mass of an electron.
Second Method––––––––––––––––––––
We can compare the masses by making the same exponents to the base 10.
We would make the powers of 10 as −31 for both the masses.
For proton's mass 1.67×10−27, to make the exponent of 10 as −31, we need to multiply 10−4 with 10−27. And, that we can acheive by moving the decimal point in 1.6700 by 4 units to the right.
Hence,
Mass of an electron =9.1×10−31 kg
Mass of a proton =16700×10−31 kg
Now, we can compare the masses of electron and proton by comparing the respective coefficients as both the exponents of 10 are equal to −31.
The number with the larger coefficient is greater.
∵ 16700>9.1
⟹16700×10−31>9.1×10−31, i.e., the mass of proton is greater than the mass of an electron.
Therefore, option (a.) is the correct one.