Rutherford’s gold foil experiment showed that atoms are mostly empty space, with the positive charge concentrated in a nucleus. He realised this because most of the alpha particles passed straight through the piece of gold foil, with just a few deflected at huge angles. J.J Thomson was the first scientist who proposed the atom model, considered a ‘Plum pudding model.’ Later on, Rutherford introduced a new model widely accepted and considered the ‘ Nuclear model of the atom.’ Rutherford had shown his model with the help of an experiment. In his investigation, he directed high energy streams of alpha particles from a radioactive source at a thin sheet(100 nm thickness) of gold. To study the deflection of alpha particles, he placed a fluorescent screen coated with ZnS. 

Ernest Rutherford was a British physicist who is particularly famous for studying the structure of the atom. Before his famous experiment with gold foil, scientists imagined the atom as a large area of positive charge, with negative charges stuck on the outside. This was called the plum pudding model because the negative charges were like plums stuck in the positively-charged plum pudding. 

But Rutherford’s experiment, also known as the Geiger-Marsden experiment, changed everything. After the experiment, we understood that the positive charge was concentrated in the nucleus and that most of the atom is space. Let’s talk about how he did it. Most of the alpha particles went straight through the gold foil as if it weren’t even there and hit the screen at an angle of zero degrees. The further they moved around the screen, the fewer particles were found. But even then, some particles deflected at HUGE angles. 

Importance of the Rutherford experiment

Rutherford concluded the following through his experiment:

1. The positively-charged centre of an atom is the nucleus that resides in an atom’s whole mass.

2. The electrons revolve in orbit around the nucleus in circular paths. 

3. Compared to the size of an atom, the size of the nucleus is tiny.  

Rutherford’s Nuclear Model of Atom 

Based on his experiment, Rutherford put forward the model of an atom, which had the following features: 

1. A positively-charged centre in an atom is called the nucleus. Nearly all the mass of an atom resides in the nucleus. 

2. The electrons revolve around the nucleus in well-defined orbits. 

3. The size of the atom is larger compared to the size of the nucleus. Rutherford’s alpha-particle scattering experiment shows the presence of a nucleus in the atom. 

His (Rutherford’s) experiment gave an important feature about the nucleus of an atom, which was also termed the nuclear model of an atom. 

1. A positively charged substance is inside the atom, termed the nucleus. 
2. The nucleus of an atom is very dense and hard.
3. Its size is tiny compared to an atom’s size. 

Conclusion of Rutherford’s scattering experiment : 

1. Most alpha particles passed through the gold foil without deflection. Rutherford concluded that most of the space in an atom is empty. 
2. Few alpha particles get deflected from their path, indicating that a positive charge occupies very little space of an atom.
3. Few alpha particles get deflected by large angles, which indicates that an atom’s whole mass and positive charge are concentrated in a small volume. 
4. From the data, he also calculated that the radius of the nucleus is about 105 times less than the radius of the atom.