How Do We Describe the Electronic Structure of Atoms

Shells are divided into subshells designated by the letters s, p, d, and f, and within these subshells, electrons are grouped in orbitals (Table 1.1). An orbital is a region of space that can hold 2 electrons. In this course, we focus on compounds of carbon with hydrogen, oxygen, and nitrogen, all of which use only electrons in s and p orbitals for covalent bonding. Therefore, we are concerned primarily with s and p orbitals. 

Fourth shell (32 electrons) Third shell (18 electrons) Second shell (8 electrons) First shell (2 electrons) 

A schematic view of an atom, (a) Most of the mass of an atom is concentrated in its small, dense nucleus, which has a diameter of 10 to 10 meter (m). (b) Each shell can contain up to 2n electrons, where n is the number of the shell.Thus, the first shell can hold 2 electrons, the second 8 electrons, the third 18, the fourth 32, and so on. (Table 1.1). 

Shell Orbitals Contained in Each Shell Maximum Number of Electrons Shell Can Hold Relative Energies of Electrons in Each Shell 

TABLE 1.2 Ground-State Electron Configurations for Elements 1-18  

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