Lead can be prepared from galena [lead(ii) sulfide] by first roasting the galena in oxygen gas to form lead(ii) oxide and sulfur dioxide. Heating the metal oxide with more galena forms the molten metal and more sulfur dioxide. Required:
a. Write a balanced equation for each step.
b. Write an overall balanced equation for the process.
c. How many metric tons of sulfur dioxide form for every metric ton of lead obtained?

it is stable as it is in group 0 which have full outer shells of electrons

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.