Which is always the first step in dealing with an accident in the lab?

call the emergency number, 911.
call the fire department.
notify the teacher.
read the msds information.

1.43 x 10^-11 j the guy commented the awnser just making sure u see it .

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.