2.1-1 Evolution of the Atomic Model

• Orbital diagrams explain how electrons are arranged within the atom and show the order in which electrons are placed in orbitals.
• Orbital diagrams use boxes to represent orbitals and use colors to represent sublevels s, p, d, f.
• To place electrons in orbital diagrams, electrons are represented by arrows and the direction of the arrow is used to represent electron spin.
• Orbitals can hold a maximum of two electrons.
• Within sublevels that contain multiple orbitals, one electron is placed in each orbital with parallel spins before the electrons are paired.
• Chemists use a notation called the electron configuration to indicate placement of electrons in an atom.
• The lowest energy sublevel is written first, then sublevels with increasing energies.
• The number of electrons in each sublevel is written as a superscript.
• Period 1 begins with hydrogen and helium, which have one electron in the 1 s orbital.
• Period 2 begins with lithium, which has three electrons, 1 s 2 2 s 1.
• After the 2 s orbital is filled, the 2 p orbitals are filled.
• One electron is placed in each p orbital before they are paired.
• An abbreviated configuration uses a noble gas in brackets to represent the filled electron configuration of that noble gas.
• Nitrogen has an atomic number of seven, which means it has seven electrons.
• The orbital diagram for nitrogen is drawn by drawing boxes to represent the occupied orbitals, placing a pair of electrons in the last occupied sublevel in separate orbitals, and then placing remaining electrons with opposite spins in each filled orbital.
• The quantum mechanical model of the atom describes the electron configuration of atoms in terms of main energy levels, sublevels, and orbitals, and relates this to energy.
• The angular momentum quantum number (l) indicates the specific orbital within the sublevel where the electron is found.
• The abbreviated orbital diagram for aluminum, [Ne] 3 s 2 3 p 1, is represented by the preceding noble gas being Ne, and the numbers filled in are 3 s and 3 p.
• The principal quantum number (n) indicates the energy level or shell where an atomic orbital can be found, with values ranging from 1 to infinity.
• The Lewis Structure of Ions is represented by the total number of electrons represented in a Lewis structure being equal to the sum of the numbers of valence electrons in each individual atom.
• Paramagnetism is attracted to a magnet, while diamagnetism is repelled by a magnet.
• The azimuthal quantum number (l) represents the kind and shape of the orbital (s, p, d, f) that is being occupied by an electron, specifying the sublevel or subshell within a particular principal energy level.
• The magnetic quantum number (m) indicates the specific orbital within the sublevel where the electron is found.
• The spin quantum number (s) describes the intrinsic spin of the electron in the orbital.
• Atoms with unpaired electrons are called paramagnetic, while atoms with paired electrons are called diamagnetic.
• The total number of electrons represented in a Lewis structure is equal to the sum of the numbers of valence electrons in each individual atom.
• The orbital diagram for aluminum, [Ne] 3 s 2 3 p 1, is represented by the numbers filled in being 3 s, 3 p, and the last electron added to the 3 p sublevel.
• Every electron in an atom is assigned a unique set of quantum numbers.