Science Change of Atoms

Ancient Greek

-Democritus was a Greek philosopher (470-380 B.C.) who is the father of modern atomic thought. - proposed that matter could NOT be -divided into smaller pieces forever. -claimed that matter was made of small, hard particles that he called "atomos" -Aristotle was a famous Greek philosopher who did not believe in Democritus' idea of atoms. -proposed that matter was made of 4 elements: earth, fire, air, water. -Although Aristotle's theory was incorrect, the power of his reputation made his theory last for over 2000 years!

Plum Pudding (Thompson)

-J.J. Thomson discovered the electron. -He also proposed the existence of a (+) particle... -His atomic model was known as the "plum pudding model"... -He was the first scientist to show that the atom was made of even smaller atoms -Atoms are made mostly out of a (+)charged material, like dough in bread. The (-) charged electrons are found inside the (+) dough.

John Dalton Atomic Theory

-John Dalton created the very first atomic theory. -Dalton viewed atoms as tiny, solid spheres. -Dalton was an English school teacher who performed many experiments on atoms. - His atomic theory had 4 statements. 1. Atoms are tiny, invisible particles. 2. Atoms of one element are all the same. 3. Atoms of different elements are different. 4. Compounds form by combining atoms.

Rutherford Atom

-Rutherford discovered protons and the nucleus. -He showed that atoms have (+) particles in the center, and are mostly empty space. -He called these (+) particles protons. -He called the center of atoms the nucleus. -used the gold foil experiment -Most α particles went through the gold. The atom is mostly empty space. -Some particles deflected and others even bounced back... this was crazy! -The atom had a very dense (+) center. Rutherford called it the nucleus.

Modern Atomic Model (quantum model)

-Work done since 1920 has changed the model. -The Heisenberg Uncertainty Principle states that it's impossible to know where an electron is at any given time. -The new atomic model has electrons moving around the nucleus in the cloud

Bohr Model

-proposed that electrons move around the nucleus in specific energy levels -Every atom has a specific number of energy levels.