When a highly reactive metal, such as magnesium (Mg), is mixed with a reactive nonmetal such as sulfur (S), the two elements will most likely combine to form a new substance, magnesium sulfide (MgS).
Based on the trends of the periodic table, which other element is likely to combine with magnesium?
A. Sodium (Na)
B. Helium (He)
C. Oxygen (O)
D. Gold (Au)

the correct answer to this question is 2

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.  

the correct answer would be b) volume versus temperature, because they are also directly proportional.