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27 Co Cobalt 58.9331944

Cobalt

TRANSITION METAL
Bohr Model: Electrons arranged in energy shells around the nucleus.

Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt in the Earth's crust is found only in chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal.

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Quick Facts

Atomic Number 27
Period 4
Group 9
Phase Solid
Appearance hard lustrous gray metal
About Transition Metals

Transition metals are elements with partially filled d-orbitals. They are hard, have high melting points, and often form colored compounds.

History

Discovered By Georg Brandt
Named By Unknown

Physical Properties

Atomic Mass 58.9331944
Density 8.9 g/L
Molar Heat 24.81 J/(mol·K)
Phase Transition (Melting & Boiling Points)

Cobalt melts at 1768 K and boils at 3200 K.

Atomic Properties

Electron Config [Ar] 3d7 4s2
Electronegativity 1.88
Electron Affinity 63.898 kJ/mol
Ionization Energy 760.4 kJ/mol
Orbital Filling Diagram
This diagram visualizes electron configuration according to the Aufbau principle and Hund's rule. Boxes represent orbitals (s, p, d, f), while arrows indicate electrons with spin up or down. Electrons fill lower energy levels first and occupy orbitals singly before pairing.

Photograph

Image of Cobalt Source: Wikipedia

External Resources

Wikipedia PubChem Royal Society of Chemistry Periodic Videos (YouTube)

Study Guide

Atomic Number

The number of protons in the nucleus, which defines the element.

Atomic Mass

The average mass of an atom, including protons and neutrons.

Electronegativity

A measure of how strongly an atom attracts electrons in a bond.

Ionization Energy

The energy required to remove an electron from an atom.

Electron Config

The arrangement of electrons in the atom's energy shells.