Mercury (Hg)

Atomic Model Details

Mercury (Hg) is a d-block element and a transition metal (though often considered a post-transition metal due to its filled d-orbital).

Fundamental Particles

Atomic Number (Z): 80
- Number of Protons: 80
- Number of Electrons: 80 (in a neutral atom)
Mass Number (A): Approximately 200.59 (average atomic mass)
- Common Isotope Hg-202: Number of Neutrons = 202 - 80 = 122

Atomic Size

Metallic Radius: Approximately 151 picometers (pm) or 1.51 Å.
Van der Waals Radius: Approximately 155 pm.

Electronic Configuration & Shell Diagram

Ground State Electronic Configuration

The electronic configuration of Mercury (Hg) is: [Xe] 4f¹⁴ 5d¹⁰ 6s²

This configuration indicates a completely filled 5d subshell and a filled 6s subshell, contributing to its unique properties and reluctance to participate in metallic bonding compared to other transition metals.

Shell-wise Electron Distribution

The electrons are distributed in principal energy shells (K, L, M, N, O, P) as follows:

K-shell (n=1): 2 electrons (1s²)
L-shell (n=2): 8 electrons (2s² 2p⁶)
M-shell (n=3): 18 electrons (3s² 3p⁶ 3d¹⁰)
N-shell (n=4): 32 electrons (4s² 4p⁶ 4d¹⁰ 4f¹⁴)
O-shell (n=5): 18 electrons (5s² 5p⁶ 5d¹⁰)
P-shell (n=6): 2 electrons (6s²)

This arrangement shows that the outermost shell (P-shell) has two electrons, while the inner 5d subshell is completely filled.

Periodic Trends

Ionization Enthalpy (IE₁)

First Ionization Enthalpy: 1007.1 kJ/mol.
- Mercury has a relatively high first ionization enthalpy for a metal. This is attributed to the very stable, fully filled 5d¹⁰ 6s² electronic configuration and significant relativistic effects that cause the 6s electrons to be held more tightly by the nucleus.

Electronegativity

Pauling Scale Electronegativity: 2.00.
- This value is higher than many other metals, reflecting its tendency to hold onto its electrons and its sometimes covalent-like bonding behavior in certain compounds.

Electron Gain Enthalpy (EGE)

Electron Gain Enthalpy: Approximately +61.3 kJ/mol.
- Mercury has a positive (endothermic) electron gain enthalpy, indicating that it does not readily accept an additional electron. This is consistent with its stable, filled valence shell configuration (6s²).

Atomic Radius

Metallic Radius: 151 pm.
- Compared to elements like Cadmium (Cd) in the same group, Mercury exhibits a slightly smaller or comparable atomic radius due to the lanthanide contraction effect, where the poorly shielding 4f electrons lead to a greater effective nuclear charge.

Key Physical Properties

Density

Density: 13.534 g/cm³ at 25 °C.
- Mercury is one of the densest elements at room temperature, second only to some other heavy metals like Osmium and Iridium.

State

State at STP: Liquid.
- Mercury is the only metallic element that is liquid at standard temperature and pressure (STP). This unusual property is due to weak metallic bonding resulting from its filled 5d¹⁰ 6s² configuration and relativistic effects.

Color

Color: Silvery-white.
- It has a characteristic metallic luster.

Melting Point

Melting Point: -38.83 °C.
- This extremely low melting point is responsible for its liquid state at room temperature.

Boiling Point

Boiling Point: 356.73 °C.
- While its melting point is very low, its boiling point is relatively high, indicating a wide liquid range.

Mercury (Hg) - Atomic Structure & Chemical Properties