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The Development of Atomic Theory

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Page 1: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

The Development of Atomic Theory

Page 2: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

10.1 The Nature of Matter

Matter is a term used to describe anything that has mass and takes up space.Greek philosophers Democritus and Leucippus proposed that matter is made of tiny particles called atoms. Atoms were an idea that few believed.The first evidence was called Brownian motion for Robert Brown, who first noticed the jerky motion of tiny particles.(1827)

Page 3: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

DemocritusAtom from the Greek word

atomos that means indivisible

Page 4: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Democritus

Proposed that all atoms are small hard particles made of a single material

Different shapes and sizes

Atoms are always moving

They form different materials by joining together

Page 5: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

John Dalton(1803)

All substances are made of atoms.

Atoms are small particles that cannot be created, divided, or destroyed.

Atoms of the same element are exactly alike (1803)

The solid sphere model - like a sour ball

Page 6: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

An early model

In 1897 English physicist J. J. Thomson discovered that electricity passing through a gas caused the gas to give off particles that were too small to be atoms.

These negative particles were eventually called “electrons.”

Page 7: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Plum –Pudding Model-Chocolate Chip Cookie

ModelThe atom is mostly positively charged material.

Electrons are small, negatively charged particles located throughout the positive material.

Proved atoms can be divided into smaller parts

Page 8: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Ernest Rutherford

Designed an experiment to test Thomson’s theory.

Proposed that in the center of the atom is a tiny dense positively charged region called the nucleus.

Tootsie roll pop

Page 9: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Rutherford’s Gold Foil Experiment

He aimed a beam of small positively

charged particles at a sheet of gold foil.The particles were larger than protons.

Page 10: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

The nuclear model

In 1911, Ernest Rutherford, Hans Geiger, and Ernest Marsden did a clever experiment to test Thomson’s model. We now know that every atom has a tiny nucleus, which contains more than 99% of the atom’s mass.

Page 11: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Bohr’s Model of the Atom

Electrons travel in definite paths around the nucleus. These paths are located in levels at certain distances from the nucleus

Gob stopper model

Page 12: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Bohr ModelA Planetary Model of the Atom

                                                                                

Page 13: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Erwin Schrodinger and Werner Heisenberg

Ferrero Rocher Model

They explained the nature of electrons in an atom

Page 14: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Electrons and the Periodic Table

Order of filling levels

Page 15: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Energy levels

These levels are divided into smaller regions called orbitals.

These regions are designated by the following letters

s,p,d and f

Page 16: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Orbitals

s- can hold 2 electrons

p- can hold 6 electrons

d- can hold 10 electrons

f- can hold 14 electrons

Page 17: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

Orbitals

The Atomic Orbitals Atom in a Box

Real-Time Visualization of the Quantum Mechanical Atomic Orbitals The orbital images on this page represent the shape of the atomic orbitals. The clouds you see are the probability distribution of an electron bound to a Hydrogen nucleus.

                                              

Page 18: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

The Modern Atomic Theory

Electrons do not travel in definite paths as Bohr had suggested

The exact path of a moving electron cannot be predicted.

Electron clouds are regions inside the atom where electrons are likely to be found

Page 19: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

10.1 Atoms

A single atom is the smallest particle that retains the chemical identity of the element.

Page 20: The Development of Atomic Theory. 10.1 The Nature of Matter Matter is a term used to describe anything that has mass and takes up space. Greek philosophers

10.1 Molecules

A molecule is a group of two or more atoms joined together chemically.