Atomic Number
27
Element 27
Cobalt (Co)
Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt is found in the Earth's crust only in chemically combined form, save for small deposits found in alloys of natural meteoric iron.
Atomic Mass
58.933 u
Category
Transition Metal
Period
4
Group
Group 9: cobalt group
Phase
solid
Density
8.9 g/cm3
Electron Shells
2, 8, 15, 2
Atomic Structure
Protons: 27. Electrons: 27. Neutrons: Varies by isotope.
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷
Why Cobalt Matters
Cobalt helps connect atomic number 27, transition metal behavior, period 4 trends, and electron shell structure. Its solid phase, atomic mass of 58.933 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷ make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Cobalt was discovered 1735 by Georg Brandt. Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt is found in the Earth's crust only in chemically combined form, save for small deposits found in alloys of natural meteoric iron.
Safety and Handling Context
Cobalt is presented here for learning and comparison. Pure elements and laboratory compounds can have hazards that depend on dose, form, and setting.
Related Elements
Frequently Asked Questions
- What is the atomic number of Cobalt?
- Cobalt has atomic number 27, which means a neutral atom has 27 protons and 27 electrons.
- What is the chemical symbol for Cobalt?
- The chemical symbol for Cobalt is Co.
- What category is Cobalt in?
- Cobalt is classified as a transition metal and sits in period 4 of the periodic table.
Explore Cobalt in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Cobalt to neighboring elements without losing your place.