What measure/number is the periodic table built on?

the periodic table built on to arranging the atomic elements into columns and rows. Atomic elements in the same columns and rows have certain properties in common.

> b takes place in the gas phase in an isothermal tubular reactor. the feed is one mole of a per one mole of c, an inert. the entering temperature and pressure are 427°c and 10 atm, respectively. the gas constant r = 0.08206 atm · l/mol · k.