Sort these elements into pairs that would most likely exhibit similar chemical properties. it doesn't matter which pair goes in which box, so long as the correct elements are paired. na, o, ne, se, rb, kr

                          Na = Rb                           Ne = Kr                           O = Se

Explanation:

According to modern periodic table, the elements present in same group have same chemical properties , because they same valence shell electrons.

Na and Rb:

As these both elements are present in group one, so these are called Alkali metals. Almost all alkali metal have same chemical properties.

Ne and Kr:

Both these elements are present in group 18, called as noble gases.They have same chemical properties like both are stable and are inert.

O and Se:

Both elements are present in group 16. Both have same chemical properties. Both have same valence shell electrons.