Scientists Major Contribution to the Atom Save Groups

Coach Finley's Chemistry Class

Who proposed that matter is made of tiny particles called atomos?

Democritus

What did Democritus believe about the divisibility of matter?

Matter could not be created, destroyed, or further divided.

What did Aristotle reject?

The notion of atoms

Why did Aristotle reject the notion of atoms?

It did not agree with his own ideas about nature

What did Aristotle believe about empty space?

He believed empty space could not exist

According to Aristotle, what is matter made of?

Earth, fire, and water

Who proposed that matter is composed of extremely small particles called atoms?

John Dalton

What did John Dalton state about atoms in terms of visibility and destructibility?

Atoms are invisible and indestructible.

According to John Dalton, what is true about atoms of a given element?

Atoms of a given element are identical in size, mass, and chemical properties.

How do atoms of a specific element compare to atoms of another element according to Dalton's theory?

Atoms of a specific element are different from atoms of another element.

In Dalton's atomic theory, how do different atoms combine to form compounds?

Different atoms combine in simple whole-number ratios.

What happens to atoms during a chemical reaction according to John Dalton?

Atoms are separated, combined, or rearranged.

Who is Sir William Crookes?

Sir William Crookes was a British chemist and physicist.

What did Sir William Crookes discover in a cathode-ray tube?

He noticed a flash of light.

What was the significance of Crookes' discovery of the cathode ray?

It led to the invention of the television.

What is a television essentially based on?

A cathode-ray tube.

Who identified the first subatomic particle?

JJ Thomson

What did JJ Thomson conclude about the mass of the charged particle compared to a hydrogen atom?

The mass of the charged particle was much less than that of a hydrogen atom.

Who determined the charge of an electron?

Robert Millikan

What apparatus did Robert Millikan use to determine the charge of an electron?

Oil-drop apparatus

What is the charge of a single electron?

1-

Who proposed the plum pudding model of the atom?

JJ Thomson

What does the plum pudding model of the atom consist of?

A spherically shaped atom composed of uniformly distributed positive charge with negatively charged electrons.

What did Ernest Rutherford conclude about the atom's positive charge and mass?

Almost all of the atom's positive charge and almost all of its mass are contained in a tiny, dense region called the nucleus.

What term did Ernest Rutherford use to describe the center of the atom?

Nucleus

What did Rutherford conclude about the particles contained in the nucleus by 1920?

The nucleus contained positively charged particles called protons.

What did James Chadwick discover in 1932?

He discovered the neutron.

What type of particle did James Chadwick identify in the nucleus?

He identified the neutron, a subatomic neutral particle.

Who discovered that an element contains a unique positive charge in its nucleus?

Henry Moseley

What identifies an atom as a particular element?

The number of protons in its nucleus.