Explain the principle of infrared spectroscopy.

Explanation:

IR (infrared) spectroscopy theory is based on the concept that the molecules tend to absorb some specific amount of the frequencies of light which are characteristic of corresponding structure of molecules. These energies are reliant on shape of molecular surfaces, associated vibration coupling, and mass corresponding to atoms.

It is used to detect the type of the functional group present in the organic compound.

3

explanation:

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