4.3 How are Electrons Distributed in Different Orbits (Shells)?

Description

Quick Overview

The section discusses how electrons are distributed within different energy levels or shells of an atom, primarily based on the rules provided by the Bohr-Bury model.

Standard

This section outlines the distribution of electrons in various shells around the nucleus of an atom. It introduces the concept of energy levels and explains how the maximum number of electrons in each shell is determined, as well as the filling order of these shells, highlighting the significance of a filled outermost shell in terms of chemical stability.

Detailed

Detailed Summary

In this section, we explore how electrons are arranged in an atom's orbits, which are also referred to as shells. The distribution of electrons is foundational in understanding atomic structure and chemical behavior. The Bohr and Bury models provide the framework for this understanding by introducing key rules for electron configuration in shells.

Key Points:

  1. Shell Designation: Electrons occupy shells designated by letters (K, L, M, N) or numbers (n=1, 2, 3, 4).
  2. Maximum Electrons per Shell: The maximum number of electrons in a shell is defined by the formula: \(2n^2\), where \(n\) represents the shell number. For example:
  3. K-shell (n=1): 2 electrons
  4. L-shell (n=2): 8 electrons
  5. M-shell (n=3): 18 electrons
  6. N-shell (n=4): 32 electrons
  7. Filling Sequence: Electrons fill inner shells before outer ones; each shell must be filled before moving to the next outer shell. This follows the principle of energy minimization, leading to stability.
  8. Valency and Stability: The outermost shell's electron capacity is crucial. Atoms tend to be more stable with a full outermost shell, which typically accommodates 8 electrons (an octet). This is reflected in the valency, or combining capacity, of atoms.
  9. Application: Understanding electron distribution allows for the prediction of chemical reactivity and the formation of compounds based on the tendency of atoms to lose, gain, or share electrons to achieve stability.

Key Concepts

  • Shells in atoms are designated as K, L, M, N.

  • Maximum electrons in a shell are calculated using 2nĀ².

  • Electrons fill inner shells before outer shells.

  • A full outer shell contributes to an atom's stability and determines its valency.

Memory Aids

šŸŽµ Rhymes Time

  • Electrons in their shells swirl, K to L, M to N in a dance and twirl!

šŸ“– Fascinating Stories

  • Picture an atom as a little house. The innermost rooms (inner shells) need to be filled before building an extension (outer shells). Only then does the house look complete!

šŸ§  Other Memory Gems

  • For remembering electron capacities: 'Kites Leave Me Nostalgic' - K(2), L(8), M(18), N(32)!

šŸŽÆ Super Acronyms

SFE - Shells Fill Electronically, meaning they fill the inner ones first.

Examples

  • The maximum number of electrons in the K-shell is 2, while in the L-shell it is 8.

  • Sodium has one electron in its outer shell, resulting in a valency of 1.

Glossary of Terms

  • Term: Electron Shell

    Definition:

    The defined regions around an atom's nucleus where electrons can be found.

  • Term: Valency

    Definition:

    The combining capacity of an atom, determined by the number of electrons in its outermost shell.

  • Term: BohrBury Model

    Definition:

    A model describing how electrons are arranged in shells around the nucleus based on specific rules.

  • Term: Energy Level

    Definition:

    The quantized level of energy that an electron can possess in the atom.