How Are Electrons Distributed In Different Orbits?

Key Notes:

Structure of the Atom:

• Atoms consist of a central nucleus surrounded by electrons.
• The electrons revolve around the nucleus in specific paths called orbits or shells.

Energy Levels (Shells):

• Electrons occupy fixed energy levels around the nucleus, designated as K, L, M, N, etc.
• These energy levels are numbered as n = 1, 2, 3, 4, and so on.

Bohr’s Model of the Atom:

• Proposed by Niels Bohr, it suggests that electrons move in specific orbits with fixed energy.
• Electrons in lower orbits have less energy, while those in higher orbits have more energy.

Maximum Number of Electrons in a Shell:

• The number of electrons each shell can hold is determined by the formula 2n², where ‘n’ is the orbit number.
  • K shell (n=1): 2 electrons
  • L shell (n=2): 8 electrons
  • M shell (n=3): 18 electrons
  • N shell (n=4): 32 electrons

Filling of Electrons in Shells:

• Electrons fill the shells in order of increasing energy (from K to N).
• Lower energy levels are filled first before moving to higher levels.

Octet Rule:

• Atoms tend to fill their outermost shell to achieve a stable configuration with 8 electrons, similar to noble gases.
• Elements with less than 8 electrons in their outer shell are reactive.

Valence Electrons:

• Electrons in the outermost shell are called valence electrons.
• These determine the chemical properties of an element.

Example of Electron Distribution:

• Carbon (Atomic number = 6): 2 electrons in K shell, 4 electrons in L shell (2, 4)
• Sodium (Atomic number = 11): 2 electrons in K shell, 8 in L shell, 1 in M shell (2, 8, 1)

Stability and Reactivity:

• Atoms are most stable when their outermost shell is completely filled.
• Atoms with incomplete outer shells will gain, lose, or share electrons to achieve stability.

Let’s practice!