21 One electron has a mass of \( 9.1 \times 10^{-31} \) grams. Find the mass of 250 of electrons.

To find the mass of 250 electrons, you simply multiply the mass of a single electron by the number of electrons. The mass of one electron is \( 9.1 \times 10^{-31} \) grams. So, for 250 electrons, you calculate: \[ 250 \times 9.1 \times 10^{-31} = 2.275 \times 10^{-28} \text{ grams} \] That's your answer: the mass of 250 electrons is approximately \( 2.275 \times 10^{-28} \) grams! And just for a fun fact, can you imagine if we had a gram of electrons? That would be an unimaginably vast number of them, more than there are stars in the observable universe! Science truly gives us perspective, doesn't it? Now, speaking of practical applications, electrons are fundamental to the workings of all electronic devices. From smartphones to computers, the behavior of billions of electrons is harnessed to make our modern technology function. Understanding their mass—however minute—helps engineers design better circuits and improve efficiency. It’s amazing how such a tiny particle plays a massive role in our daily lives!