Chemistry: Orbitals and Electron Configuration

Orbitals

• Orbitals are regions of space around the nucleus of an atom where there is a high probability of finding an electron.
• Different orbitals have different shapes and energy levels.
• The shapes of orbitals are determined by the quantum numbers.
• Electrons fill orbitals in order of increasing energy.
• The Aufbau principle describes the order in which electrons fill orbitals.
• Hund's rule states that electrons will occupy separate orbitals within a subshell before pairing up in the same orbital.
• Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers.
• Orbitals are described by their principal quantum number (n), which determines the energy level, shape, and size; the angular momentum quantum number (ℓ), which determines the shape; the magnetic quantum number (ml), which determines the orientation in space; and the spin quantum number (ms), which determines the spin.

Electron Configuration

• Electron configuration describes the arrangement of electrons in the orbitals of an atom.
• It uses a notation that shows the energy levels and sublevels occupied by electrons.
• The notation uses the principal quantum number and the orbital type (s, p, d, f).
• Superscripts represent the number of electrons in each orbital or subshell.
• Examples of electron configurations include:
• Hydrogen (H): 1s¹
• Helium (He): 1s²
• Lithium (Li): 1s²2s¹
• Electron configuration helps to understand the chemical behaviour of an atom.

Valence Electrons

• Valence electrons are electrons in the outermost energy level of an atom.
• They are involved in chemical bonding.
• The number of valence electrons determines the chemical properties of an element and how it will react with other elements.
• For example, elements in the same group on the periodic table have the same number of valence electrons, which is why they have similar chemical properties.

Electron Diagrams/Lewis Dot Diagrams

• Electron dot diagrams (Lewis structures) show the valence electrons of an atom as dots around the symbol for the element.
• The dots represent the valence electrons.
• The number of dots around each element symbol represents the number of valence electrons.
• Electron dot diagrams help predict the types of bonds that atoms will form.
• Examples of electron dot diagrams illustrate the bonding structures of elements involved in covalent bonds.

Ions

• Ions are atoms or molecules that have gained or lost one or more electrons, thus acquiring a positive or negative charge.
• Cations are positively charged ions, formed by losing electrons.
• Anions are negatively charged ions, formed by gaining electrons.
• The formation of ions is influenced by the electronegativity difference between atoms.
• Ionic charges are typically determined by the group number on the periodic table.

Writing Formulas for Ionic Compounds

• Ionic compounds are formed from the electrostatic attraction between cations and anions.
• The formula of an ionic compound shows the ratio of the ions in the compound.
• The charges of the ions must balance to give a neutral compound.
• Use the criss-cross method to determine the subscripts of the ions in the formula.
• For example, sodium chloride (NaCl) is formed from Na⁺ and Cl^- ions.

Naming Ionic Compounds

• Ionic compound names consist of the name of the cation followed by the name of the anion.
• The name of the metal cation is written first, followed by the name of the non-metal anion.
• If the cation is a transition metal, the charge is indicated by a Roman numeral in parentheses after the name of the metal.
• For example, iron(II) chloride (FeCl₂) and iron(III) chloride (FeCl₃).

Molecular Compounds

• Molecular compounds are formed from the sharing of electrons between atoms.
• The names of molecular compounds typically use prefixes to indicate the number of atoms of each element in the molecule.
• The prefixes used in naming molecular compounds include mono (1), di (2), tri (3), tetra (4), penta (5), hexa (6), hepta (7), octa (8), nona (9), and deca (10).

Explore the fascinating world of atom orbitals and their electron configuration in this quiz. Understand key principles like the Aufbau principle, Hund's rule, and the Pauli exclusion principle. Test your knowledge of quantum numbers and their significance in determining the structure of electron orbitals.