Explain why metal powder is used instead of large piece of metal

The surface area increases, thus increasing the rate of reaction

Explanation:

When you use powder instead of solid metal, the surface area to volume ratio increases and so does the rate of reaction, because the chance of collisions between the particles increases as they can "touch" the metal more easily when it is looser, like powder.

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of carbon is as shown here in the image.

the answer for sodium is 0.186

the answer for rubidium is 0.251