What is the "magic number' of valence electrons? How does this influence the type of bonds formed by various combinations of
elements

Magic number is any number in electron shells that suggest stability. It corresponds to total number of electrons in filled electron shells.

If an electron is having magic number, then it forms stable bonds.

Explanation:

The magic numbers are 2,10,18,36,54, 86 and 126. This refers to the total number of electrons that an electron can have when it is completely filled.

Atomic nuclei which carries either of these nucleons have high binding energy as compared to others. Hence, they have high stability. Bonds in such elements are more strong.

Radioactive decay of such elements is very slow.

Eugene Winger coined the term "magic number".

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.