What family has the most reactive metals give an example (symbol and name)

The elements of Group 1 (the alkali metals) have the most reactive metals.

Cesium (Cs) is so reactive that it reacts explosively with water.

beta decay is the answer

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.