Difference Between 1s and 2s Orbital

Key Difference – 1s vs 2s Orbital
 

Atom is the smallest unit of matter. In other words, all matter is made out of atoms. An atom is composed of subatomic particles, mainly, protons, electrons, and neutrons. Protons and electrons make the nucleus, which is located at the center of the atom. But electrons are positioned in orbitals (or energy levels) which are located outside the nucleus of an atom. It is also important to note that orbitals are hypothetical concepts which are used to explain the most likely location of an atom. There are various orbitals surrounding the nucleus. There are also sub-orbitals such as s, p, d, f, etc. The s sub-orbital is spherical in shape when considered as a 3D structure. The s orbital has the highest probability of finding an electron around the nucleus. A sub-orbital is again numbered as 1s, 2s, 3s, etc. according to the energy levels. The key difference between 1s and 2s orbital is the energy of each orbital. 1s orbital has a lower energy than the 2s orbital.

CONTENTS
1. Overview and Key Difference
2. What is 1s Orbital
3. What is 2s Orbital
4. Side by Side Comparison – 1s vs 2s Orbital
5. Summary

What is 1s Orbital?

1s orbital is the orbital that is closest to the nucleus. It has the lowest energy among other orbitals. It is also the smallest spherical shape. Therefore, the radius of s orbital is small. There can be only 2 electrons in the s orbital. The electron configuration can be written as 1s¹, if there is only one electron in the s orbital. But if there is a pair of electrons, it can be written as 1s². Then the two electrons in the s orbital move to the opposite directions because of the repulsion that occurs due to the same electrical charges of the two electrons. When there is an unpaired electron, it is called paramagnetic. That is because it can be attracted by a magnet. But if the orbital is filled and a pair of electrons are present, the electrons cannot be attracted by a magnet; this is known as diamagnetic.

What is 2s Orbital?

The 2s orbital is larger than 1s orbital. Hence, its radius is larger than that of the 1s orbital. It is the next closet orbital to the nucleus after 1s orbital. Its energy is higher than 1s orbital but is lower than other orbitals in an atom. 2s orbital also can be filled only with one or two electrons. But 2s orbital is filled with electrons only after the completion of 1s orbital. This is called Aufbau principle, which indicates the order of electron filling into sub-orbitals.

What is the difference between 1s and 2s Orbital?

Summary – 1s vs 2s Orbital

An atom is a 3D structure containing a nucleus at the center surrounded by variously shaped orbitals of different energy levels. These orbitals are again divided into sub-orbitals according to slight differences of energy. Electrons, which is a major subatomic particle of an atom is located in these energy levels. 1s and 2s sub-orbitals are nearest to the nucleus. The main difference between 1s and 2s orbitals is the difference of their energy level, which is, 2s orbital is a higher energy level than 1s orbital.

Reference:
1. Libretexts. “Atomic Orbitals.” Chemistry LibreTexts. Libretexts, 03 Nov. 2015. Web. 26 May 2017. <https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Electronic_Structure_of_Atoms_and_Molecules/Atomic_Orbitals>.
2. Atoms, Electrons and Orbitals. N.p., n.d. Web. 26 May 2017. <http://www.mhhe.com/physsci/chemistry/carey/student/olc/ch01atoms.html>.

Image Courtesy:
1. “S orbitals” (cropped) By CK-12 Foundation – File:High School Chemistry.pdf, page 265 (CC BY-SA 3.0) via Commons Wikimedia