What is the atomic number of lead?

Lead has atomic number 82, meaning its nucleus contains 82 protons. It is in Period 6, Group 14 of the periodic table and is the heaviest stable element.

What is the electron configuration of lead?

Lead has the full electron configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p². Its two 6p valence electrons and two 6s electrons (which behave as an inert pair) give lead its characteristic +2 and +4 oxidation states.

Why does lead symbol Pb not match its English name?

The symbol Pb comes from the Latin word "plumbum," the ancient Roman name for lead. The English word "lead" has Germanic roots, but the chemical symbol retained the Latin form, which is also the origin of the word "plumber" (Roman pipe-fitters used lead pipes).

What are the common oxidation states of lead?

Lead most commonly forms the +2 oxidation state (Pb²⁺), due to the inert pair effect where the 6s² electrons resist participation in bonding. The +4 state (Pb⁴⁺) also exists but is strongly oxidizing and less stable. Negative oxidation states are rare.

How many stable isotopes does lead have?

Lead has four stable isotopes: ²⁰⁴Pb (1.4%), ²⁰⁶Pb (24.1%), ²⁰⁷Pb (22.1%), and ²⁰⁸Pb (52.4%). The last three are radiogenic end products of the uranium-235, uranium-238, and thorium-232 decay chains respectively, so their abundance varies in geological samples.

Yes, lead is a heavy metal toxin. Even small amounts of lead exposure can cause serious neurological damage, particularly in children. It accumulates in the body (especially in bones) and disrupts haem synthesis, nerve signal transmission, and kidney function. This is why lead has been largely phased out of paints, fuels, and water pipes.

Lead Element Properties

Name: Lead Element Properties
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Author: Nham Vu

Complete reference for Lead (Pb, element 82): atomic data, electron configuration, isotopes, physical constants, and chemical behavior.

82 Pb 207.2

Lead

Post-transition Metal — Period 6, Group 14

Atomic Identity

Atomic Number

Symbol

(from Latin plumbum)

Standard Atomic Wt.

207.2 u

IUPAC 2021

Period

Group

IVA

Block

p-block

CAS Number

7439-92-1

Pb metal

Discovery

Known since antiquity

pre-history

Latin name

Plumbum

origin of symbol Pb

Electron Configuration

Full notation 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p²

Noble gas shorthand [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p²

Electrons per shell 2, 8, 18, 32, 18, 4

Valence electrons 4 (6s² 6p²)

Unpaired electrons 2 (in 6p)

Spin multiplicity 3 (triplet)

Orbital Diagram (Valence Shell)

—

Diamagnetic

2 unpaired electrons in 6p (inert pair effect in 6s)

Notable Isotopes of Lead

Isotope	Protons	Neutrons	Mass (u)	Natural Abundance	Stability / Origin
²⁰⁴Pb	82	122	203.97304	1.4%	Stable Stable — primordial
²⁰⁶Pb	82	124	205.97447	24.1%	Stable Stable — end product of ²³⁸U decay chain
²⁰⁷Pb	82	125	206.97590	22.1%	Stable Stable — end product of ²³⁵U decay chain
²⁰⁸Pb	82	126	207.97667	52.4%	Stable Stable — end product of ²³²Th decay chain
²¹⁰Pb	82	128	209.98419	Trace	Unstable Radioactive — β⁻, t½ = 22.3 yr (²³⁸U chain)
²¹²Pb	82	130	211.98867	Trace	Unstable Radioactive — β⁻, t½ = 10.64 h

²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb are radiogenic — their abundance varies in geological samples depending on local uranium and thorium content. Lead-208 is doubly magic (82 protons, 126 neutrons).

Physical Properties

State at STP Solid (metal)

Appearance Bluish-gray, lustrous when fresh

Density (20 °C) 11.34 g/cm³

Density (liquid, at mp) 10.66 g/cm³

Melting Point 327.46 °C (600.61 K)

Boiling Point 1749 °C (2022 K)

Heat of Fusion 4.77 kJ/mol

Heat of Vaporization 179.5 kJ/mol

Specific Heat (25 °C) 26.650 J/(mol·K)

Thermal Conductivity 35.3 W/(m·K)

Electrical Resistivity 208 nΩ·m (20 °C)

Hardness (Mohs) 1.5

Chemical Properties

Electronegativity (Pauling) 1.87

Electron Affinity 35.12 kJ/mol

1st Ionization Energy 715.6 kJ/mol

2nd Ionization Energy 1450.5 kJ/mol

3rd Ionization Energy 3081.5 kJ/mol

4th Ionization Energy 4083 kJ/mol

Covalent Radius 146 pm

Van der Waals Radius 202 pm

Oxidation States +2 (dominant), +4, +1 (rare), -4 (rare)

Crystal Structure Face-centered cubic (FCC)

Lattice Constant (a) 495.1 pm

Magnetic Ordering Diamagnetic

Ground State Quantum Numbers

Principal (n) 6 (outermost electrons)

Azimuthal (l) 1 (p orbital)

Magnetic (mₗ) +1, 0, or −1

Spin (mₛ) +½ and +½ (two 6p electrons)

Term symbol ³P₀

Degeneracy 1

Core configuration [Xe] 4f¹⁴ 5d¹⁰ 6s²

Key Spectral Emission Lines

405.78 nm (Violet)

Pb I resonance line — strong optical

368.35 nm (UV-near)

Pb I — widely used in AAS analysis

283.31 nm (UV)

Pb I — primary AAS analytical line

261.42 nm (Deep UV)

Pb II — ionized lead line

220.35 nm (Deep UV)

Pb II — high-sensitivity detection

1278.8 nm (NIR)

Pb I — near-infrared transition

Key Facts About Lead

Heaviest Stable Element

Lead (Z=82) is the heaviest element with at least one stable isotope. All elements with atomic number above 82 (bismuth and beyond) are radioactive. Lead-208 is a doubly magic nucleus with 82 protons and 126 neutrons, giving it exceptional nuclear stability.

Inert Pair Effect

The 6s² electron pair in lead resists involvement in bonding due to relativistic contraction — the 6s orbital is pulled closer to the nucleus at high atomic numbers. This "inert pair effect" makes Pb²⁺ far more stable than Pb⁴⁺ and explains why lead prefers a +2 oxidation state.

Radiometric Dating Endpoint

Lead isotopes ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb are the stable end products of uranium-238, uranium-235, and thorium-232 decay chains respectively. Measuring their ratios in minerals enables uranium-lead dating — one of the most precise geochronological methods, dating rocks up to 4.5 billion years old.

Radiation Shielding

Lead is the standard material for shielding against X-rays and gamma radiation. Its high density (11.34 g/cm³) and high atomic number give it exceptional photon attenuation coefficients. Lead aprons, bricks, and glass are used in hospitals, nuclear facilities, and research laboratories worldwide.

Ancient Metal

Lead has been used since at least 6500 BCE — among the earliest metals exploited by humans. The Romans used it extensively for water pipes, vessels, and cooking utensils. The Latin word "plumbum" survives today in the chemical symbol Pb and in "plumber," reflecting centuries of lead pipe usage.

Significant Toxicity

Lead is a cumulative toxin that affects the nervous, hematopoietic, renal, and reproductive systems. It mimics calcium and zinc in biological pathways. Despite this, it remains essential in lead-acid batteries (automotive), radiation shielding, and some specialist alloys where no adequate substitute yet exists.

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Summary