The pressure of a sample of helium is 4.5 atm in a 300. mL container. If the container is compressed to 200. mL without changing the temperature, what is the new pressure (in atm)?

i just learnt this recently but i need to look through my notes again

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.