Quick Start

Install mendeleev (see Installation for details):

pip install mendeleev

Or with visualization support:

pip install mendeleev[vis]

All examples below work after pip install mendeleev. No database download needed — it ships with the package.

1. Get an element by symbol

from mendeleev import element

si = element("Si")
print(si.name)           # Silicon
print(si.atomic_number)  # 14

2. Get an element by name or atomic number

from mendeleev import element

al = element("Aluminium")   # by name
o  = element(8)             # by atomic number
print(al.atomic_number)     # 13
print(o.name)               # Oxygen

3. Import elements directly by symbol

from mendeleev import Fe, O, H

print(Fe.name)           # Iron
print(H.atomic_weight)   # 1.008

4. Get multiple elements at once

from mendeleev import element

c, h, o = element(["C", "Hydrogen", 8])
print(c.name, h.name, o.name)  # Carbon Hydrogen Oxygen

5. Access element properties

from mendeleev import element

si = element("Si")
print(f"Atomic weight:      {si.atomic_weight}  Da")
print(f"Melting point:      {si.melting_point}  K")
print(f"Boiling point:      {si.boiling_point}  K")
print(f"Density:            {si.density}        g/cm³")
print(f"Electronegativity:  {si.en_pauling}")
print(f"Electron affinity:  {si.electron_affinity}  eV")

6. Work with isotopes

from mendeleev import element

carbon = element("C")
for iso in carbon.isotopes:
    print(f"C-{iso.mass_number}: {iso.abundance}%")
# C-12: 98.93%
# C-13: 1.07%

Access a specific isotope directly:

from mendeleev import isotope

c14 = isotope("C", 14)
print(f"Half-life: {c14.half_life} years")  # 5700.0

7. Bulk data with pandas

from mendeleev import fetch_table

df = fetch_table("elements")
print(df[["symbol", "name", "atomic_number", "atomic_weight"]].head())

# Filter and sort
heavy = df[df["atomic_number"] > 80]
print(heavy[["symbol", "name", "density"]].sort_values("density", ascending=False))

8. Create a visualization

from mendeleev.vis import periodic_table

# Interactive plot (requires bokeh or plotly)
periodic_table(colorby="atomic_radius", backend="plotly")

# Save a static plot
periodic_table(colorby="en_pauling", backend="seaborn", output="en_periodic.png")

9. Work with ions

from mendeleev.ion import Ion

fe2 = Ion("Fe", charge=2)
fe3 = Ion("Fe", charge=3)
print(f"Ionic radius Fe²⁺: {fe2.ionic_radius} pm")
print(f"Ionic radius Fe³⁺: {fe3.ionic_radius} pm")

10. Compare electronegativity scales

from mendeleev import fetch_electronegativities

# `scales` selects computed scales; stored scales
# (Pauling, Allen, Ghosh, ...) are always included as columns
en = fetch_electronegativities(scales=["mulliken"])
print(en[en["symbol"] == "Si"])

Or access scales directly on an element:

from mendeleev import element

si = element("Si")
print(si.en_pauling)       # 1.9
print(si.en_allen)         # 11.33
print(si.electronegativity(scale="mulliken"))    # computed on the fly

11. Access properties with units

from mendeleev import Fe, Al

# Append _u to any property for a pint Quantity
print(Fe.atomic_weight_u)   # 55.845 dalton
print(Al.melting_point_u)   # 933.47 kelvin

# Convert units easily
print(Al.melting_point_u.to("celsius"))  # 660.32 degree_Celsius

12. Use the CLI

element.py Si           # by symbol
element.py 14           # by atomic number
element.py Silicon      # by name

Prints all available properties in the terminal (installed with the package).

What next?