# (Handwritten) Atoms notes and important topics for boards class 12 physics

All the matter in the universe is made up of atoms, but what exactly is an atom ? or what is the shape of this atom ? To answer all these queries, different experiment was conducted in history to find what will be the shape of an atom and what does it consist off ?

Well, this chapter 12 Atoms of class 12th Physics answer all these problems and in this article we are going to give you an overview of the chapter.

As well as if you are a class 12th student then this article will be helpful for you because we will be giving you important topics and in-depth notes for your class 12th board exam.

As I told you that different experiments were conducted in the ’80s and 90’s to find more about this atom such as its shape and structure and one of these famous experiments was Geiger and Marsden experiment or commonly known as Rutherford’s gold foil experiment.

## First Step in finding the shape of an atom:

In this experiment alpha particle (α) is passed through a gold foil and due to this, alpha particle are deflected and a flash of light can be seen on a screen around the gold foil.

You can see the animated version of this experiment in the following image:

Here is a real-life example of how this experiment looks like

So Rutherford’s experiment actually showcases these two things in the experiment:

1. Most of the alpha particles are passed straight without deviation within 1°.

2. You will notice in the experiment that a very small part actually get reflected or deflected (1 out of 8000)

So we are not going into the detail of this experiment because the important part is the conclusion we derive from this experiment regarding the structure and shape of an atom.

### The conclusion from the Rutherford’s experiment for an atom:

1. Space in the atom is mostly empty because only 1 out of 8000 actually gets reflected at 180°.

2. This experiment suggests that all the positively charged particles are together at one location in the centre. It is the “Nucleus”.
So the nucleus has all the positive charge and mass, therefore, it has the capacity to reflect α particle.

## Important Topics:

Important topics from Atoms for boards are Electron Orbit, Atomic Spectra, Bohr’s Model and Postulate, Energy Level and de Broglie explanation.

For 1 marker and MCQ for class 12th boards, conceptual questions from these topics as well as Gold foil experiment can be asked.

All these topics are provided in the notes given below, they are highly in-depth of class 12th Physics notes of Atoms so refer to them, it’s more than enough for boards.

## Handwritten notes

This article is a brief summary of chapter 12 Atoms. For all the derivation related to this chapter and other important things. I have prepared my special handwritten notes. These notes have all the derivation of this chapter and important topics for your board exam 🙂