Organic Chemistry Chapter 1: Atomic Bonding and Isomerism

Study Notes

Electron Arrangement in Atoms

Electrons are concentrated in certain regions of space around the nucleus called orbitals.
Each orbital can contain a maximum of two electrons.
Orbitals are grouped in shells designated by the numbers 1, 2, 3, and so on.
Each shell contains different types and numbers of orbitals, corresponding to the shell number.
For example, shell 1 contains only one type of orbital, designated the 1s orbital.
Shell 2 contains two types of orbitals, 2s and 2p, and shell 3 contains three types, 3s, 3p, and 3d.
Within a particular shell, the number of s, p, and d orbitals is 1, 3, and 5, respectively.

Importance of Valence Electrons

Filled shells play almost no role in chemical bonding.
The outer electrons, or valence electrons, are mainly involved in chemical bonding.
The valence electrons are the electrons in the outermost shell of an atom.
The element's symbol stands for the kernel of the element (the nucleus plus the filled electron shells), and the dots represent the valence electrons.

Periodic Table and Valence Electrons

The elements are arranged in groups according to the periodic table.
The group numbers correspond to the number of valence electrons (except for helium).

Atomic Structure

An atom consists of a small, dense nucleus containing positively charged protons and neutral neutrons.
The nucleus is surrounded by negatively charged electrons.
The atomic number of an element equals the number of protons in its nucleus.
The atomic weight is the sum of the number of protons and neutrons in its nucleus.

Outlook

Electrons are located in orbitals, which are grouped in shells.
An orbital can hold a maximum of two electrons.
Valence electrons are located in the outermost shell.
The kernel of the atom contains the nucleus and the inner electrons.

Ionic and Covalent Bonding

Gilbert Newton Lewis proposed a theory of chemical bonding in 1916.
He noticed that inert gas helium had only two electrons surrounding its nucleus and that the next inert gas, neon, had 10 such electrons.
He concluded that atoms of these gases must have very stable electron arrangements because these elements do not combine with other atoms.

Description

This chapter introduces the basics of atomic bonding and isomerism, focusing on the arrangement of electrons in atoms and their role in forming molecules. It covers the concept of orbitals and electron arrangements in lighter elements.