# Atomic Structure

Man’s curiosity about the universe is limitless. While trying to understand how the world works, we began to ponder into the constituent particles of the matter around us. We began to cut matter into smaller and smaller pieces, from molecules to atoms.

## What is atomic structure?

Several physicists and chemists like John Dalton, Niels Bohr, Ernest Rutherford, and J. J. Thomson came up with certain theories for the atomic structure of matter, of which some failed to justify their behavior and properties. Atom’s, which were once believed to be the smallest constituting particles of the matter proposed by John Dalton with his atomic theory, was found to consist of 3 subatomic particles, each particle with its own distinct properties summing up to a stable atomic structure model.

#### Definition

The atomic structure of a substance can be defined as the structure of an atom consisting of the positively charged nucleus which is neutralized by negatively charged particles at varying distances from the nucleus.

### Sub-Atomic Particles

The subatomic particles mentioned in daltons atomic model are Protons, Electrons and Neutrons.

#### 1.Proton

• Proton is positively charged subatomic particles.
• Mass of a proton is 1.6727 x 10-24
• For ease of calculations,
• We use amu (Atomic Mass Unit) [ 1 amu = 1.6605 x 10-24 g]
• So, the mass of a proton in amu is 1.007316.

#### 2. Neutron

• Neutrons are particles with zero effective charge i.e neither positive nor negative.
• Mass of a neutron is 1.6750 x 10-24 g which is 1.008701 amu.

#### 3. Electron

• An electron is the negatively charged subatomic particle.
• Mass of an electron is 9.110 x 10-28 g which is 0.000549 amu.

### Protons, Neutrons & Electrons

From the data, we can see that:

Protons and Neutrons have similar masses of 1 amu whereas the mass of an Electron is 2000 times lighter.

While explaining about atomic structure, Neutrons and Protons are held together rather closely in the center of an atom. Together they make up the nucleus, which accounts for almost all of the mass of the atom.

Whereas, electrons which are in constant motion around the nucleus, constitute almost the entire volume of the atom.

The negatively charged electron is attracted to the positively charged nucleus by a Coulombic attraction. Whereas, protons and neutrons are held together in the nucleus by the strong nuclear forces.

The chemical reactivity of an element is primarily based on the number of electrons in the atom of that element. The elements reactivity also depends on the effective charge of the atom wherein the effective charge is the sum of the number of protons to electrons.

Given below is the atomic structure of an oxygen atom with 8 electrons, 8 protons, and 8 neutrons. Here we can see that the electrons occupy the outer shell layers, whereas the protons and neutrons can be found in the nucleus.

### Atomic Structure Examples

Let us now look at atomic structures of some elements.

### Atomic Models

Based on the technology available at the time, different theorists, physicists and chemists came up with different proposals on how the constituent particles of an element are present inside it. They are:

Moreover, with today’s technology, it has been found that the subatomic particles namely protons, neutrons, and electrons have constituent particles, called Quarks and Gluons. Quarks and Gluons are the building blocks for larger particles, but they show varied properties compared to their larger particle counterparts which are a discussion for high-level particle physicists. To learn more topics, register with BYJU’S