Astatine Bohr Model, Electron Shell Diagram
Visualize the exact electron shell distribution of Astatine (At). Its 85 total electrons orbit the microscopic nucleus across 6 quantum energy shells in the specific mathematical pattern 2 – 8 – 18 – 32 – 18 – 7.
Live Bohr Shell Diagram
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Astatine Nuclear Composition
Protons, neutrons, and electrons at a glance
Protons
85
Positive charge carriers in the nucleus
Neutrons
125
Neutral mass carriers in the nucleus
Electrons
85
Across 6 shells: 2-8-18-32-18-7
Detailed Bohr Model Analysis
Astatine's traditional Bohr model diagram provides a spectacular two-dimensional blueprint of its subatomic structure. By plotting its 85 negatively charged electrons rotating around a positively charged nucleus (containing 85 protons and approximately 125 neutrons), we can visually decrypt its chemical properties.Across its 6 electron shells, Astatine distributes its electrons in the following exact hierarchical sequence, from the innermost ring outward: 2 – 8 – 18 – 32 – 18 – 7.
Applying the Bohr Rules to Astatine
The Bohr model, introduced by Niels Bohr in 1913, radically changed our understanding of atomic structure by proposing that electrons orbit the nucleus in strictly quantized circular energy levels (or 'shells'). For Astatine, we apply the 2n² rule, which states that the maximum electron capacity of any given shell is determined by two times the shell number (n) squared.In the case of Astatine, its 85 total electrons stack outward from the nucleus. The innermost K-shell (n=1) holds 2 electrons. The L-shell (n=2) holds 8. This stacking continues geometrically until we map the entire 2 – 8 – 18 – 32 – 18 – 7 sequence. Because Astatine is a high-mass transuranic or deep-period element, its inner shells are packed with immense density—holding up to 32 electrons in a single shell. This massive inner core creates a powerful electrostatic shield, severely shielding the outermost electrons from the nucleus and introducing complex relativistic contraction.
The Role of Astatine's Valence Electrons
When analyzing the Bohr model of Astatine, the absolute most critical ring is the outermost shell. This layer holds exactly 7 valence electrons.In chemistry, the core electrons (the inner rings) are chemically inert. They do not participate in bonding. All chemical reactivity, covalent sharing, and ionic transfers are conducted exclusively by the valence electrons. Because Astatine has 7 valence electrons, it inherently seeks to achieve a stable "octet" (a full outer shell of 8 electrons, or 2 for lightweight elements). Holding more than 4 valence electrons means Astatine is highly electronegative. It aggressively steals or shares electrons from surrounding elements to perfectly complete its outer ring, typically forming strong covalent bonds or electronegative anions.
Bohr Shell Rules (Quick Reference)
- 2n² Rule: Shell n holds a maximum of 2n² electrons.
- Octet Rule: The outermost (valence) shell holds a max of 8 electrons for chemical stability.
- Aufbau Order: Electrons fill from innermost shell outward.
- Valence = Reactivity: The electrons in the last shell dictate how the element bonds.
Chemical & Physical Overview
The element Astatine, represented universally by the chemical symbol At, holds the atomic number 85. This means that a standard neutral atom of Astatine possesses exactly 85 protons within its dense nucleus, orbited precisely by 85 electrons. With a standard atomic weight of approximately 210.000 atomic mass units (u), Astatine is classified fundamentally as a halogen.
From a periodic standpoint, Astatine resides in Period 6 and Group 17 of the periodic table, placing it firmly within the p-block. The overarching category of an element—whether it behaves as an alkali metal, a halogen, a noble gas, or a transition metal—is determined exclusively by how these electrons fill the available quantum shells.
Diving deeper into its physical footprint, Astatine exhibits a calculated atomic radius of 150 picometers (pm). When attempting to physically remove an electron from its outermost shell, it requires a primary ionization energy of 9.317 eV. Furthermore, its tendency to attract shared electrons in a covalent chemical bond—known as its electronegativity—measures at 2.2 on the Pauling scale. These specific subatomic metrics (radius, ionization, and electron affinity) combine to define exactly how Astatine interacts, bonds, and reacts with every other chemical element in the observable universe.
Atomic Properties — Astatine
Atomic Mass
210 u
Electronegativity
2.2 (Pauling)
Block / Group
P-block, Group 17
Period
Period 6
Atomic Radius
150 pm
Ionization Energy
9.317 eV
Electron Affinity
2.8 eV
Category
Halogen
Oxidation States
Real-World Applications
Real-World Applications & Industrial Uses
The distinct electronic structure of Astatine directly empowers its functionality in the physical world. Its specific combination of atomic radius, electron affinity, and valence shell configuration makes it absolutely indispensable across modern industry, biological systems, and advanced technology.Here are the primary real-world applications of Astatine:
Without the specific quantum mechanics occurring microscopically within Astatine's electron cloud, these macroscopic technologies and biological processes would fundamentally fail to operate.
Did You Know?
The rarest naturally occurring element on Earth — at any given time only around 28 grams (~1 oz) exists in the entire planet's crust. All isotopes are radioactive with short half-lives. Astatine-211 is a highly promising targeted alpha therapy (TAT) agent for cancer, as alpha particles are lethal to cancer cells while sparing surrounding tissue.Shell-by-Shell Capacity Table
How each of Astatine's 6 shells compare to their theoretical maximum
| Shell | Symbol | Electrons (This Element) | Max Capacity (2n²) | Fill % |
|---|---|---|---|---|
| 1 | K (n=1) | 2 | 2 | 100% |
| 2 | L (n=2) | 8 | 8 | 100% |
| 3 | M (n=3) | 18 | 18 | 100% |
| 4 | N (n=4) | 32 | 32 | 100% |
| 5 | O (n=5) | 18 | 50 | 36% |
| 6 | P (n=6) | 7 | 72 | 10% |
Shell Comparison: Astatine vs Neighbors
⬤ Current
At
Astatine
Z=85
2-8-18-32-18-7 shells
Explore Other Atomic Models of Astatine
Frequently Asked Questions — Astatine Bohr Model
Bohr Models for All 118 Elements
Toni Tuyishimire
Toni is specialized in high-performance computational tools and complex STEM visualizations. Through Toni Tech Solution, he architects scientifically accurate, deterministic software systems designed to educate and empower global digital audiences.