The Structureof the Atom:

A Journey Inside the Atom

In this image made by a scanning tunneling microscope (STM), individual silicon atoms on the surface of a silicon crystal are seen at a magnification of 10 million.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

For example:

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

Democritus - 460 B.C.

develop the idea of atoms

For example:

He asked this question: If you break a piece of matter in half, and then break it in half again, how many

breaks will you have to make before you can break it no further?

Democritus thought that it ended at some point, a smallest possible bit

of matter. He called these basic matter particles, atoms.

The Beginning

• Aristotle (384 – 322 BC)

• Aristotle dismissed the atomic idea as worthless.

• Aristotle was very popular.

The Beginning

• Aristotle (384 – 322 BC)

The End of The Beginning

• Aristotle dismissed the atomic idea as worthless.

• Aristotle was very popular.

• The idea of atoms was forgotten.

• People are gullible.

John Dalton1) All matter is made of atoms. Atoms are indivisible and indestructible.

(1766-1844)

2) All atoms of a given element are identical in mass and properties

3) Compounds are formed by a combination of two or more different kinds of atoms.

4) A chemical reaction is a rearrangement of atoms.

Model of Atom At This Point:

Atoms are thought of as

little solid spheres.

The Electrical Nature of MatterThe Wimshurst Machines (1700’s)

The Electrical Nature of MatterThe Leyden Jar (1745)

The Electrical Nature of Matter

“The Electrified Boy”

The Electrical Nature of Matter

The “Electrified Woman”

“Zapping” a tooth ache

The Electrical Nature of MatterIt Became Dangerous!

Musschenbroek held in one hand this jar, while with the other he attempted to draw sparks from the barrel. Suddenly he received a shock in the hand holding the jar, that shook him like a stroke of lightning, and for a moment made him believe that

"he was done for.

When it is electrified strongly, I can take it into another room and there fire spirits of wine with it. If while it is electrifying I put my finger, or a piece of gold which I hold in my hand, to the nail, I receive a shock which stuns my arms and shoulders. (von Kleist)

St. Petersburg, 6 August 1783. Prof. Richman and his assistant being struck by lightning while charging capacitors. The assistant escaped almost unharmed, whereas Richman was dead immediately. The pathologic analysis revealed that "he only had a small hole in his forehead, a burnt left shoe and a blue spot at his foot. [...] the brain being ok, the front part of the lung sane, but the rear being brown and black of blood." The conclusion was that the electric discharge had taken its way through Richmann's body. The scientific community was shocked.

J.J. Thomson’s Plum Pudding1897

This Model of the atom explained the electrical nature of matter.

Other Atomic Discoveries

Max Planck 1900 : If atoms vibrate strong enough, such as when you heat an object until it glows, you can measure the light energy given off - only in discrete units. He called these energy packets, quanta.

• Physicists at the time thought that light consisted of waves but, according to Albert Einstein, the quanta behaved like discrete particles. Physicists call Einstein's discrete light particle, a "photon*."

• Atoms not only emit photons, but they can also absorb them. In 1905, Albert Einstein wrote a ground-breaking paper that explained that light absorption can release electrons from atoms, a phenomenon called the "photoelectric effect." Einstein received his only Nobel Prize for physics in 1921 for his work on the photoelectric effect.

Other Atomic Discoveries

Other particles got discovered around this time (1900) called alpha rays. These particles had a positive charge and physicists thought that they consisted of the positive parts of the Thompson atom (now known as the nucleus of atoms).

Other Atomic Discoveries

Rutherford’s Gold Foil ExperimentIn 1911 Ernest Rutherford thought it would prove interesting to bombard atoms with these alpha rays, figuring that this experiment could investigate the inside of the atom (sort of like a probe). He used Radium as the source of the alpha particles and shined them onto the atoms in gold foil. Behind the foil sat a fluorescent screen for which he could observe the alpha particles impact.

Rutherford’s Gold Foil Experiment

Expected results with Thomson’s Plum Pudding Model:

Alpha particles go through with little

deflection

Actual results:Most alpha particles

Go through, but some are DRASTICALLY

deflected

Not until 1919 did Rutherford finally identify the particles of the nucleus as discrete positive charges of matter. Using alpha particles as bullets, Rutherford knocked hydrogen nuclei out of atoms of six elements: boron, fluorine, sodium, aluminum, phosphorus, an nitrogen. He named them protons, from the Greek for 'first', for they consisted of the first identified building blocks of the nuclei of all elements. He found the protons mass at 1,836 times as great as the mass of the electron.

Other Atomic Discoveries

The Nuclear ModelNucleus contains protons (+) and neutrons (neutral), or nucleons.

Protons and neutrons are the same mass

Electrons (-) cruise around the nucleus

Electrons are MUCH smaller than the other nucleons (protons and neutrons)

If the nucleus was the size of an orange, the whole atom would be the size of a football stadium.

Relative Sizes: If protons and neutrons were the size of marbles.

The actual size of the atom would be similar to a football stadium.

Atomic Numbernumber of protons

Atomic Massprotons + neutrons(average isotopes)

proton (+)

neutron

electron (-)+ + +

+ + +-

- -

-

--

Atomic Numbernumber of protons

Atomic Massprotons + neutrons(average isotopes)

proton (+)

neutron

electron (-)+ + +

+ + +-

-

-

--

1+

Atomic Numbernumber of protons

Atomic Massprotons + neutrons(average isotopes)

proton (+)

neutron

electron (-)+ + +

+ + +

-

-

--

2+

Atomic Numbernumber of protons

Atomic Massprotons + neutrons(average isotopes)

proton (+)

neutron

electron (-)+ + +

+ + +

-

-

--

4-

-

-

-

-

-

-

Relative Masses

That is… If an electron weighed eight pounds and 6 ounces…

Neutron = 1.6749286 x 10-27 kgProton = 1.6726231 x 10-27 kgElectron = 9.1093897 x 10-31 kg

A proton or a neutron would weigh 15,400 lbs

A Male African Elephant

protons and neutrons would have a diameter as large as the Burj Dubai Tower (1,830 feet and growing).

Electrons were the size of a basketball…

.

Relative Sizes

If a solid piece of steel was 10 feet by 10 feet and 12 miles long…

The actual MATTER that is contained in that steel has the volume of one grain of rice!

Relative Sizes

Fun Density Facts:

One cm3 of water has a mass of… - 1.0 grams

One cm3 of gold has a mass of… - 19.3 grams

One cm3 of protons has a mass of…

One cm3 of iridium has a mass of… - 22.7 grams

One cm3 of lead has a mass of… - 11.3 grams

1 cm3 = about the volume of

- 1,500,000,000,000,000 grams

Nissan “Cube”1,134,000 grams

The Great Pyramid of Gaza: Mass of 6 x 1012 grams

That’s the mass of 250 of these:

Nucleus - Protons - Neutrons

Empty Space - with an occasional electron

In the nuclear model of the atom… - 99.99% of the atom’s matter is in the nucleus - 99.99% of the atom’s volume is empty space - Nearly ALL matter is mostly empty space.

How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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How Come We Can’t Go Through Stuff?

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Remember: - Opposite charges attract - Like charges repel

That “empty space” has negatively charged electrons cruising around

How Come We Can’t Go Through Stuff?

Finger

Table

Remember: - Opposite charges attract - Like charges repel

That “empty space” has negatively charged electrons cruising around

Summary Facts1) Protons and Neutrons make up the nucleus (center) of the atom.

3) Electrons are VERY small compared to protons and neutrons.

5) The nucleus (protons and neutrons) are pieces of matter that are more dense than you can friggin’ imagine.

4) The electron cloud is GI-NORMOUS compared to the nucleus.

2) Electrons move really fast, making a “cloud” around the nucleus.

7) Matter is primarily made up of NOTHING! (Empty Space)

8) We can’t go through solid matter, because the electron clouds repel us before we can touch it.

6) The electrons can be rubbed off or added to the outside layer of an atom

Summary Questions1) What particles make up an atom?

2) How are those particles arranged within the atom?

3) What charge does each of the nuclear particles have?

4) Arrange the particles from smallest to largest?

Other Stuff• But there appeared something terribly wrong with

Rutherford's model of the atom. The theory of electricity and magnetism predicted that opposite charges attract each other and the electrons should gradually lose energy and spiral inward. Moreover, physicists reasoned that the atoms should give off a rainbow of colors as they do so. But no experiment could verify this rainbow.

• In 1912 a Danish physicist, Niels Bohr came up with a theory that said the electrons do not spiral into the nucleus and came up with some rules for what does happen. (This began a new approach to science because for the first time rules had to fit the observation regardless of how they conflicted with the theories of the time.)

• Bohr said, "Here's some rules that seem impossible, but they describe the way atoms operate, so let's pretend they're correct and use them." Bohr came up with two rules which agreed with experiment:

• RULE 1: Electrons can orbit only at certain allowed distances from the nucleus.

• RULE 2: Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. Also, an atom absorbs energy when an electron gets boosted from a low-energy orbit to a high-energy orbit.

• Light (photons) emit whenever an electron jumps from one orbit to another. The jumps seem to happen instantaneously without moving through a trajectory.

• The examples above show only two possibilities from Rule 2.

Numerous Scientists showed that the electron arrangement is not that simple, but it was a great starting point.

“Nucleon”

Not until 1932 did the English physicist James Chadwick finally discover the neutron. He found it to measure slightly heavier than the proton with a mass of 1840 electrons and with no charge (neutral). The proton-neutron together, received the name, "nucleon."