Lithium (Li)

Atomic Model Details of Lithium (Li)

Element Symbol: Li
Atomic Number (Z): 3
- Number of Protons: 3
- Number of Electrons: 3 (in a neutral atom)
Mass Number (A): Approximately 7 (for the most common isotope, Lithium-7)
- Number of Neutrons: 4 (Mass Number - Atomic Number = 7 - 3)
Atomic Size (Metallic Radius): 152 pm

Electronic Configuration: 1s² 2s¹
Shell Diagram Representation:
- K-shell (1st shell): Contains 2 electrons (fully filled).
- L-shell (2nd shell): Contains 1 electron (valence electron).
- This configuration indicates that Lithium has one electron in its outermost shell (valence shell), making it highly reactive and prone to losing this electron to form a +1 ion.

First Ionization Enthalpy (IE₁): 520.2 kJ/mol
- This is the energy required to remove the single valence electron. Being an alkali metal, Lithium has a relatively low first ionization enthalpy compared to elements in the same period, but higher than other alkali metals below it in Group 1.
Electronegativity (Pauling Scale): 0.98
- Lithium has a low electronegativity, indicating its tendency to lose electrons rather than attract them in a chemical bond.
Electron Gain Enthalpy: +59.6 kJ/mol
- The positive value indicates that energy must be supplied to add an electron to a neutral Lithium atom, signifying its metallic character and low tendency to accept electrons.
Atomic Radius: 152 pm
- As the first element in Group 1, Lithium has the smallest atomic radius among the alkali metals.

Density: 0.534 g/cm³ (at 20°C)
- Lithium is the lightest known metal.
State at Standard Temperature and Pressure (STP): Solid
Color: Silvery-white (when freshly cut, rapidly tarnishes in air to a dull grey or black due to oxide formation).
Melting Point: 180.5 °C
- Lithium has a relatively low melting point for a metal, but it is the highest among the alkali metals.
Boiling Point: 1342 °C