1.3 Atomic Properties
2026-02-10 20:26
Status: #developing
Tags: #chemistry #cram #atoms
Atomic Properties
General Ideas
- AMU:
of a Carbon-12 atom in mass and ~ 1 proton or neutron in mass - Isotope: atoms of the same element with different masses
- Atomic Mass
- Actual measurement of mass for an element-isotope
- Average atomic mass is the weighted averages for all isotopes based on abundance
- Octet Rule
- Atoms are in a full or empty valence shell when in their most stable configuration
- Metallic
- More likely to form a cation
- Energy levels
- eV difference between shells, difference is lower at higher shells
Atomic Forces
- Atomic Radius - distance from nucleus to valence shell
- Shielding Effect
- Repulsion from inner shell electrons that push outer shell electrons away from the nucleus
- Effective nuclear change
- Net attraction force from nucleus on the valence electrons after subtracting the shielding effect
Ionization energy (IE)
- Energy increase for an atom as it loses a valence electron (cation).
- Periodic table trend - Top right
- Lower IE is preferred among atoms
- More IE = less stable atom
Electron affinity
- Energy change for an atom as it gains an electron (anion)
- Atoms want this to be as high as possible
- Periodic table trend - top right
Basic Quantum Mechanics
Hierarchy of Quantum Organization
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- Shell (eV levels)
- 1-7 levels (corresponds to periodic table period)
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- Subshell (type of orbital)
- S, p, d, f types
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- Orbitals
- Contains 2 electrons
-
- Spin direction of Electrons
Up, Down - Up spin electrons are prioritized first when working in subshell organization
Electron Configuration
- Describes the SPDF relationship of an atom.
- Uses SPDF periodic trends
- Short hand configuration
- [Noble Gas] Electron configuration of next period
- SPDF blocks in correspondence to period
- S = period
- P = period
- D = period - 1
- F = period - 2
Isoelectronic
- Same electron configuration but different element
- An ion with an isoelectronic configuration that of a noble gas is stable