Atomic Number
20
Element 20
Calcium (Ca)
Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft gray Group 2 alkaline earth metal, fifth-most-abundant element by mass in the Earth's crust.
Atomic Mass
40.078 u
Category
Alkaline Earth Metal
Period
4
Group
Group 2: alkaline earth metals
Phase
solid
Density
1.55 g/cm3
Electron Shells
2, 8, 8, 2
Atomic Structure
Protons: 20. Electrons: 20. Neutrons: Varies by isotope.
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
Why Calcium Matters
Calcium helps connect atomic number 20, alkaline earth metal behavior, period 4 trends, and electron shell structure. Its solid phase, atomic mass of 40.078 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Calcium was discovered 1808 by Humphry Davy. Calcium is a chemical element with symbol Ca and atomic number 20. Calcium is a soft gray Group 2 alkaline earth metal, fifth-most-abundant element by mass in the Earth's crust.
Safety and Handling Context
Calcium 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 Calcium?
- Calcium has atomic number 20, which means a neutral atom has 20 protons and 20 electrons.
- What is the chemical symbol for Calcium?
- The chemical symbol for Calcium is Ca.
- What category is Calcium in?
- Calcium is classified as a alkaline earth metal and sits in period 4 of the periodic table.
Explore Calcium in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Calcium to neighboring elements without losing your place.