Atomic Number
34
Element 34
Selenium (Se)
Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium.
Atomic Mass
78.971 u
Category
Nonmetal
Period
4
Group
Group 16: oxygen group
Phase
solid
Density
4.81 g/cm3
Electron Shells
2, 8, 18, 6
Atomic Structure
Protons: 34. Electrons: 34. Neutrons: Varies by isotope.
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴
Why Selenium Matters
Selenium helps connect atomic number 34, nonmetal behavior, period 4 trends, and electron shell structure. Its solid phase, atomic mass of 78.971 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴ make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Selenium was discovered 1817 by Jöns Jakob Berzelius. Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium.
Safety and Handling Context
Selenium 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 Selenium?
- Selenium has atomic number 34, which means a neutral atom has 34 protons and 34 electrons.
- What is the chemical symbol for Selenium?
- The chemical symbol for Selenium is Se.
- What category is Selenium in?
- Selenium is classified as a nonmetal and sits in period 4 of the periodic table.
Explore Selenium in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Selenium to neighboring elements without losing your place.