Gallium
Gallium (Ga, atomic number 31) is a Period 4 post-transition (p-block, 69.723 u). Melts just above room temperature at 29.76 °C (302.91 K)—liquefying in a human hand—yet remains liquid up to 2400 °C. Forms III–V direct-bandgap semiconductors (GaAs, G
Gallium is a chemical element on the periodic table with the atomic symbol Ga, atomic number 31, and standard atomic weight 69.723 u. Classified as a Post-Transition within Group 13 and Period 4 (p-block), gallium possesses a ground-state electron configuration of [Ar] 3d10 4s2 4p1 distributed across 4 concentric Bohr electron shells (2 · 8 · 18 · 3) with 3 outer-shell electrons. Melts just above room temperature at 29.76 °C (302.91 K)—liquefying in a human hand—yet remains liquid up to 2400 °C. Forms III–V direct-bandgap semiconductors (GaAs, GaN) for blue LEDs and solar cells.
⚛️ Interactive Periodic Table Lab: Explore Gallium (Ga, Z = 31) in the CRV Science Dynamic Periodic Table & Bohr Orbital Lab to visualize its animated 2 · 8 · 18 · 3 electron shells, simulate live phase transitions from 0 K to 6,000 K, and compare periodic heatmaps across all 118 IUPAC elements.
Atomic Structure and Periodic Trends: How Do Quantum Orbitals Define Gallium?
Electron Shell Architecture and Ground-State Configuration
A neutral atom of gallium contains 31 protons in its atomic nucleus balanced by 31 electrons occupying quantized atomic orbitals. In the Bohr-Sommerfeld and quantum-mechanical orbital models, these electrons populate 4 principal energy shells (K (n=1): 2e−, L (n=2): 8e−, M (n=3): 18e−, N (n=4): 3e−), terminating in the directional dumbbell-shaped p-orbital (azimuthal quantum number l = 1) with ground-state configuration [Ar] 3d10 4s2 4p1. Removing the most loosely bound valence electron from an isolated gaseous gallium atom requires a first ionization energy of 579 kJ/mol, while its tendency to attract shared bonding electrons is quantified by a Pauling electronegativity of 1.81.
Periodic Table Position and Neighboring Elements
Within the periodic table, Gallium occupies Period 4, Group 13 of the p-block (Post-Transition Metals). Along Period 4, it is flanked by Zinc (Zn, Z = 30) and Germanium (Ge, Z = 32). Vertically within its periodic family, Gallium shares valence orbital symmetry and homologous chemical trends with Aluminum (Al), Indium (In), Thallium (Tl), Nihonium (Nh). Learners can interactively compare Gallium's orbital radii, ionization energy, and Pauling electronegativity against all neighboring elements in the Dynamic Periodic Table Lab.
Physical and Thermodynamic Properties: How Does Gallium Behave Across Temperature Regimes?
Standard Phase, Melting Point, and Boiling Point Dynamics
At standard ambient temperature and pressure (298.15 K / 25 °C, 1 atm), elemental gallium exists as a crystalline solid. As thermal energy increases, its crystal or molecular lattice undergoes solid-to-liquid fusion at a melting point of 302.91 K (+29.76 °C / +85.6 °F) and transitions to the vapor phase at a normal boiling point of 2,673 K (+2399.85 °C / +4351.7 °F), spanning a liquid thermodynamic range of 2370.09 K. In the CRV Science Dynamic Periodic Table, dragging the live temperature slider between absolute zero (0 K) and solar-photosphere temperatures (6,000 K) dynamically tracks Gallium's state transitions in real time alongside enthalpy and entropy phase equilibria.
Quantitative Atomic and Thermodynamic Parameter Matrix
| Parameter | Quantitative Value / Formula | Physical / Quantum Basis | Comparative Context in Group 13 / Period 4 |
|---|---|---|---|
| Atomic Number & Symbol | Z = 31 (Ga) | 31 nuclear protons; nuclear charge +31e | Located in Period 4, Group 13 (p-block) |
| Standard Atomic Weight | 69.723 u (g/mol) | Abundance-weighted isotopic nucleon mass | ~39 neutrons in dominant/reference mass number |
| Electron Configuration | [Ar] 3d10 4s2 4p1 | Shells: 2 · 8 · 18 · 3 (3 outer-shell e−) | Post-Transition Metals valence orbital architecture |
| Electronegativity & Ionization | χ = 1.81; IE1 = 579 kJ/mol | Pauling bond polarity scale & first valence ionization enthalpy | Governs covalent vs. ionic bond character |
| Melting & Boiling Points | MP: 302.91 K; BP: 2673 K | Cohesive lattice energy and intermolecular forces | STP (298 K) phase: SOLID (Liquid range: 2370.09 K) |
| Principal Oxidation States | +3 | Valence electron donation, sharing, or acceptance | Discovered / First Isolated: 1875 |
Chemical Reactivity, Bonding, and Oxidation States: How Does Gallium Form Compounds?
Characteristic Oxidation States and Coordination Chemistry
As a p-block post-transition metal situated to the right of the d-block, its valence electrons experience incomplete nuclear shielding from filled d (and in Period 6–7, f) subshells, resulting in higher electronegativity, softer metallic lattices, and the relativistic inert-pair effect. In chemical compounds, gallium exhibits characteristic oxidation states of +3. Depending on the electronegativity difference (Δχ) of its bonding partners—such as Oxygen (χ = 3.44), Fluorine (χ = 3.98), Chlorine (χ = 3.16), Nitrogen (χ = 3.04), Carbon (χ = 2.55), or Hydrogen (χ = 2.20)—gallium forms redox-specific oxides, halides, hydrides, or coordination complexes governed by Gibbs free energy (ΔG = ΔH − TΔS).
Nucleosynthesis, Discovery History, and Elemental Origins
First identified or isolated in 1875, Gallium carries a distinct cosmological and geochemical signature. With atomic number Z = 31 beyond the iron-56 binding-energy peak, gallium is synthesized astrophysically via neutron-capture nucleosynthesis—combining slow neutron capture (the s-process in asymptotic giant branch stars) and rapid neutron capture (the r-process in neutron-star mergers and core-collapse supernovae).
Biological Role and Scientific Applications: Why Is Gallium Important in Nature and Technology?
Biochemical Classification: Abiotic / Technological / Synthetic
In comparative biochemistry and systems physiology, Gallium is classified as Abiotic / Technological / Synthetic. No known essential biological role; important in planetary geochemistry, astrophysics, materials science, or nuclear physics. Across terrestrial and marine ecosystems, its chemical speciation interacts with thermodynamics, enthalpy, entropy, chemistry.
Key Mechanistic Functions and Technological Uses
Melts just above room temperature at 29.76 °C (302.91 K)—liquefying in a human hand—yet remains liquid up to 2400 °C. Forms III–V direct-bandgap semiconductors (GaAs, GaN) for blue LEDs and solar cells. Researchers and students can further investigate Gallium's functional role alongside all 118 elements by launching the Interactive Periodic Table & Element Detective Lab on CRV Science Learn.
Frequently Asked Scientific Questions
What is the electron configuration and valence shell structure of Gallium (Ga)?
Gallium (atomic number Z = 31) has the ground-state electron configuration [Ar] 3d10 4s2 4p1, distributing its 31 electrons across 4 shells as 2 · 8 · 18 · 3. Its outermost shell contains 3 electrons, placing Gallium in Group 13, Period 4 (p-block) as a member of the Post-Transition Metals. You can watch these 31 electrons orbit the nucleus in real time in the Dynamic Periodic Table Bohr Lab.
What phase of matter is Gallium at room temperature, and when does it melt or boil?
At standard room temperature (298 K / 25 °C) and 1 atm pressure, Gallium is a crystalline solid. It melts at 302.91 K (+29.76 °C / +85.6 °F) and boils at 2,673 K (+2399.85 °C / +4351.7 °F). Using the 0–6,000 K temperature slider in the Interactive Periodic Table, you can observe Gallium's exact solid, liquid, and gas transitions relative to all other elements.
How does Gallium function in biochemistry, materials science, and technology?
Melts just above room temperature at 29.76 °C (302.91 K)—liquefying in a human hand—yet remains liquid up to 2400 °C. Forms III–V direct-bandgap semiconductors (GaAs, GaN) for blue LEDs and solar cells. In biological systems, it is categorized under Abiotic / Technological / Synthetic, with principal oxidation states of +3 and a first ionization energy of 579 kJ/mol.