Lithium

Lithium is atom number 3 — every Lithium atom has exactly 3 protons in its center, and that number is what makes it Lithium and nothing else. Its symbol is Li. At room temperature it is a solid.

Lithium (from Greek:λίθος lithos, "stone") is a chemical element with the symbol Li and atomic number 3. It is a soft, silver-white metal belonging to the alkali metal group of chemical elements. Under standard conditions it is the lightest metal and the least dense solid element.

Summary from the source dataset, derived from Wikipedia (CC BY-SA 3.0) · original article

Lithium sits in period 2, group 1 of the s-block. Its 3 electrons fill shells of 2, 1 — written as [He] 2s1. Its electronegativity is 0.98 on the Pauling scale, and pulling the first electron off takes 520.2 kJ/mol. The outermost shell holds 1 electron — the ones that do all the chemistry.

Full configuration: 1s2 2s1
Ionization energies (kJ/mol): 520.2, 7298.1, 11815
Electron affinity: 59.6326 kJ/mol · Electronegativity (Pauling): 0.98
Density: 0.534 g/cm³ · melts 453.65 K · boils 1603 K

Values exactly as published — see where the data comes from.