PERIODIC TABLE - BONDS

Electronic structure of atoms:

 Electrons move in defined (allowed) orbits around the nucleus and at fairly large distances. Electrons that move at approximately the same distance from the nucleus are said to be in the same shell or shell or energy level (figure 1.1).

1.1

When atoms are unexcited, their electrons are distributed in at most seven shells, K, L, M, N, O, P, and Q.

Each shell is characterized by a number denoted n and called the principal quantum number .

For n = 1 we have the layer closest to the core, K, for n = 2 layer L etc. As we move away from the core, the energy level of the layer increases. That is,

EK< EL< EM< ...

Distribution of electrons in layers:

For the arrangement of electrons in layers (electronic structure) we follow the following rules:

1. The maximum number of electrons that each of the first four shells is given by the formula 2n2, where n is the principal quantum number, i.e. the shell number. So K can take up to 2 electrons, L up to 8 electrons, M up to 18 electrons and N up to 32 electrons.

2. The last shell of any atom cannot have more than 8 electrons. Unless it's K which is filled with 2 electrons.

3. The penultimate shell cannot contain more than 18 electrons, but neither can it contain less than 8. Unless it is K that has at most 2.

Allocation of Shells to an Atom