Arrangement of electrons in an atom and the the periodic table

An electron is stable subatomic particle with a charge of negative electricity, found in all atoms and acting as the primary carrier of electricity in solids. This definition is according to Wikipedia. Therefore, it is obvious that electrons have something to do with electricity and atoms. The arrangement of electrons may be looked at from two points; the periodic table or in an atom. A periodictable is a table of the chemical elements arranged in order of atomic number, usually in rows, so that elements with similar atomic structure (and hence similar chemical properties) appear in vertical columns. An atom is the most fundamental or the basic unit of a chemical element.

The arrangement of electrons in a periodic table is done according to their size, mass and atomic numbers. You can learn this by watching a presentation on the same from The arrangement of electrons in the periodic table clip. Basically, the electronic structure of an element determines its position in a periodic table. Electronic structure refers to the way electrons are arranged in an atom. It is also important to note that electron affinity, the energy required or released when an electron is added to a gaseous ion or atom, normally increases going up a group and increased left to right across the periodic table. Non-metals have the tendencies of highest electron affinities.

The arrangement of electrons in an atom is commonly referred to as electron configuration. Electronic configuration occurs in various shells and sub-shells, orbits, or energy levels of an atom. Electrons are often located in the empty space outside the nucleus of an atom. Repulsions between electrons are minimised due to the way they are organised. For that reason, you will find that there is a distinct distance of up to 100,000 times away from the nucleus of an atom which are inter dispersed. There is an energy level associated with each distinct distance. To further understand how the electrons arranged, it is important to keep in mind the important rules of Bohr and Bury scheme or models.

Bohr and Bury Scheme - Important Rules

• Maximum number of electrons that can be accommodated in a shell is given by 2n2 where n = shell number
• For 1st energy level, n = 1Maximum number of electrons in 1st energy level = 2n22 x (1) 2 = 2
• For 2nd energy level n = 2Maximum number of electrons in the 2nd energy level = 2n22 x 22 = 2 x 4 = 8
• For 3rd energy level n = 3Maximum number of electrons in the 3rd energy level = 2n2= 2x(3) 2= 2 x 9 = 18
• For 4th energy level n = 4Maximum number of electrons in the 4th energy level = 2n2= 2x(4) 2= 2x16 = 32

Sl.No	Electron Shell	Maximum Capacity
1	K Shell	2 electrons
2	L Shell	8 electrons
3	M shell	18 electrons
4	N shell	32 electrons

• The outermost shell of an atom cannot accommodate more than 8 electrons, even if it has a capacity to accommodate more electrons. This is a very important rule and is also called the Octet rule. The presence of 8 electrons in the outermost shell makes the atom very stable.

*Bohr and Bury Scheme - Important Rules lifted from Tutor Vista website