Radiation, conduction, and convection are methods of energy transfer. of these methods, radiation is the only one in which energy can be transferred through

  empty space.

The other methods of energy transfer make use of the physical motion of the atoms, molecules, or bulk of the medium. Radiation moves energy via electromagnetic waves, rather than physical contact between objects or physical transfer of material.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6