What do the elements in each pair have in common? k, kr be, mg ni, tc b, ge al, pb?

The pairs are:
K, Kr - Same period
Be, Mg - Same group
Ni, Tc - Both are transition metals
B, Ge - Both are metaloids
Al, Pb - Both form inert oxides

Elements are the defined as the substances that cannot be broken down into simpler forms. Elements are arranged in the periodic table based on the similar properties they exhibit.

Given elements are:

Potassium (K), Krypton (Kr), Beryllium (Be), Magnesium (Mg), Nickel (Ni), Technetium (Tc), Boron (B), Germanium (Ge), Aluminum (Al), Lead (Pb).

The pairs that have common characteristics are:

K, Kr - Elements belong to same period 4. Be, Mg - Elements belong to dame group 2 A. Ni, Tc - Both elements are transition metals B, Ge - Both elements are metalloids Al, Pb - Both form inert oxides

Therefore, the elements are either placed in same group or period due to their similar characteristics.

To know more about elements, refer to the following link:

link

Sorry i dont understand the question can you rephase it?

The disturbance is only parallel to the motion of the wave.