Helium (He) is located in Period 1 of the periodic table.
Understanding Periodic Table Periods
The periodic table organizes elements based on their atomic number and recurring chemical properties. Elements are arranged in rows and columns. The horizontal rows are known as periods, and they indicate the number of electron shells an atom of that element typically possesses. Elements in the same period have the same highest unexcited electron energy level. The higher the period number, the more electron shells an atom has, and generally, the larger its atomic radius.
Key Properties of Helium (He)
Helium, with the atomic number 2, is a noble gas and one of the most abundant elements in the universe. Its position in Period 1 signifies that it has electrons occupying only the first energy shell.
Here's a quick overview of Helium's key properties:
| Property | Value |
|---|---|
| Element Name | Helium |
| Symbol | He |
| Atomic Number | 2 |
| Period | 1 |
| Group | 18 |
| Block | s |
| State at 20°C | Gas |
As the first element in Group 18 (the noble gases) and having only two electrons, Helium completes its outermost electron shell (the 1s subshell), making it incredibly stable and unreactive. Its placement in Period 1 means it is among the elements with the simplest atomic structures, having only one electron shell.
