INSIDE THE ATOM

By : Crystal Rodriguez& Phyllis Almaraz& Lupita Hernandez

•stated that elements consisted of tiny particles called atoms.•compounds consisted of atoms of different elements combined together.•Compounds have constant composition because they contain a fixed ratio of atoms•the reason elements were differed from one another was that atoms of each element were different from one another(they had different masses).•Compounds are pure substances because the atoms of different elements are bonded to one another somehow, and are not easily separated from one another.

Solid Sphere model

John Dalton

GREEK ATOMISM

Ancient Greek philosophers were the first to theorize about microstructure, or the idea that matter is made up of smaller pieces such as atoms.

Though Democritus carried atomic theory the farthest, his ideas are predictions and improvements on earlier Greek theories.

Democritus believed atoms were the building block of nature, and could not be created or destroyed and that all atoms were different in their structure, shape, and size.

The philosopher Aristotle disagreed with Democritus on the point of atoms. Aristotle believed that the world could not consist of small particles because air did not fall to the ground as any object did when thrown into the air.

Aristotle believed there were four basic elements: dryness, wetness, heat, and cold

THE PLUM PUDDING MODEL

J.J. Thompson showed that atoms contained small particles with a negative charge.

He named the particles electrons. The electrons were thought to be

positioned throughout the atom, but with many structures possible for positioning multiple electrons, particularly rotating rings of electrons.

Thompson knew that atoms had no charge. This meant a positive charge in the atom must be present to balance the negative charge of the electrons.

He said the negatively charged electrons were embedded in a sphere of positive charge so the charges were balanced.

J.J. Thomson

RUTHERFORD'S ALPHA PARTICLE EXPERIMENT

Rutherford fired positively charged particles called alpha particles at a thin sheet of gold foil.

The alpha particles were emitted from a sample of Uranium.

Rutherford expected all the alpha particles to go through the foil, as he believed Thompson's 'plum pudding' atomic structure.

Rutherford found that A small number of alpha particles were deflected at various angles to their initial direction, and that A small number of alpha particles rebounded off the foil back towards the sample of Uranium.

In conclusion An atom's mass must be concentrated in a small positively charged nucleus as only a very small number of alpha particles either deflected or rebounded off the foil.

Also Most of the atoms must be empty space. This space must contain the electrons.

THE NUCLEAR MODEL He developed a model of a hydrogen atom and also a

theory that states that electrons travel in certain orbits around the atom’s nucleus.

The chemical properties of an element being determined mainly by the number of electrons present.

The picture on the left is of the planetary model which was founded by Bohr and Rutherford in 1913 that shows a positive charged nucleus surrounded by electrons that orbit the nucleus

In the Bohr Model the neutrons and protons occupy a dense central region called the nucleus, and the electrons orbit the nucleus much like planets orbiting the Sun.

CONCLUSION Science has come a long way in more

than two thousand years since Democritus first proposed the idea of atoms.