Periodic Table/Arsenic

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33As74.9216 Da

Arsenic

Metalloid·Period 4, Group 15·p-block

Metalloid element of group 15. There are three allotropes, yellow, black, and grey. Reacts with halogens, concentrated oxidizing acids and hot alkalis. Albertus Magnus is believed to have been the first to isolate the element in 1250.

Gallery

Ultrapure Metallic Arsenic under Argon, 1 - 2 grams. Original size of each piece in cm: 0.5 x 1

Hi-Res Images ofChemical Elements, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, source: https://images-of-elements.com/arsenic.php

Physical Propertiesmass · density · phase · crystal

Atomic Mass

74.9216Da

Density

5.7500g/cm³

Phase (STP)

Solid

Melting Point

1090.2K

Boiling Point

889.1K

Molar Heat

0.3290J/(mol·K)

Crystal Structure

RHL

Lattice Constant

4.130Å

Atomic Radiiatomic · covalent · van der Waals

Atomic (Empirical)

115.00pm

Covalent

121.00pm

Van der Waals

185.00pm

Electronic Propertieselectronegativity · ionization · affinity

Electron Configuration

[Ar] 3d10 4s2 4p3

Electron Shells

2, 8, 18, 5

Electronegativity

2.18Pauling

Electron Affinity

0.8kJ/mol

1st Ionization Energy

9.8kJ/mol

Oxidation States

-3, +2, +3, +5

Orbital DiagramAufbau · Hund's rule · Pauli exclusion

↑↓

1s²

↑↓

2s²

↑↓

2p⁶

↑↓

3s²

↑↓

3p⁶

↑↓

3d¹⁰

↑↓

4s²

↑

4p³

Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3Short: [Ar] 3d10 4s2 4p3

Ionization Energies (33 known)

Emission Spectrumvisible range · characteristic spectral lines

614

508

495

As emission

380nm750nm

494.6 nm(100%)508.4 nm(50%)614.3 nm(30%)

Abundanceby mass

🌍Earth's Crust

1.8 ppm

🌊Ocean

3.7 ppb

✨Universe

8.0 ppb

🧬Human Body

50.0 ppb

Log scale · ppm = parts per million by mass

Biological Role

Toxic

Highly toxic — disrupts ATP production. Chronic exposure causes arsenicosis. Historic poison.

Discovery

Discovered By

Known to the ancients.

Named By

—

Year

—

Nuclear Data

Known Isotopes

Stable Isotopes

Stable Mass Numbers

60, 61, 62, 63, 75

Natural isotopic abundance (IUPAC recommended values)

Isotopes of As33 known

Nuclide	Z	N	Mass (AMU)	Half-life	Decay	Jπ	Abundance
⁶⁰Asstable	33	27	59.993945	Stable	p	5+	—
⁶¹Asstable	33	28	60.981535	Stable	p	3/2-	—
⁶²Asstable	33	29	61.973784	Stable	p	1+	—
⁶³Asstable	33	30	62.964036	Stable	p	3/2-	—
⁷⁵Asstable	33	42	74.921595	Stable	stable (1%)	3/2-	10000.0000%
⁹⁰As	33	57	89.955995	Unknown	β⁻, β⁻n, 2n	—	—
⁹¹As	33	58	90.960816	Unknown	β⁻, β⁻n, 2n	5/2-	—
⁹²As	33	59	91.967386	Unknown	β⁻, β⁻n, 2n	—	—

Click any isotope for its full page with decay chain:

⁶⁰As ⁶¹As ⁶²As ⁶³As ⁶⁴As ⁶⁵As ⁶⁶As ⁶⁷As ⁶⁸As ⁶⁹As ⁷⁰As ⁷¹As ⁷²As ⁷³As ⁷⁴As ⁷⁵As ⁷⁶As ⁷⁷As ⁷⁸As ⁷⁹As ⁸⁰As ⁸¹As ⁸²As ⁸³As ⁸⁴As ⁸⁵As ⁸⁶As ⁸⁷As ⁸⁸As ⁸⁹As ⁹⁰As ⁹¹As ⁹²As

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