Ch4 s1

4.1 Studying Atoms

Wrap: 1/22/2013 Pg 102-110

1. What are the major ideas in Democritus theory(2)?

2. What are the major ideas in Aristotle’s(2)? Who’s theory is closer to our modern understanding of matter?

3. What does Dalton’s atomic theory state (3 parts)? What part do you know is wrong?

Try:

Balance: Al2O3+ MgS Al2S3 + MgO

4.1 Studying Atoms

Wrap: 1/24/2012 Pg 106-119

1. What is an atom? Compare the number of atoms in a penny to the number of people in the world.

2. Why was Rutherford important? Draw his model of the atom

3. How is atomic number different than atomic mass. What is the atomic # and mass of V and Sg?

4. Give 2 facts each about protons, neutrons, and electrons.

How many p,n,e’s are in Tungsten?

4.1 Studying Atoms

Atomic TheoryContributions /

Theory

Experiment used/ Explain Model

Aristotle Believed everything was made of fire, air, water and earth

DO NOT DO!!

Democritus Believed everything was made of atoms

DO NOT DO!!

Dalton (Know 3 parts) DO NOT DO!!

Thomson Discovered the electron and size of electron

Used cathode ray tube- particles were attracted to positive end of magnet

Rutherford Discovered nucleus, and overall charge and volume of nucleus

Gold foil experiment-some alpha particles bounced straight back. Most went through

4.1 Studying Atoms

Elements to know by Friday Flash Cards?

• First 20 elements name and chemical symbol (H- Ca) (For Friday). Also Atomic Theory

• Also Cr, Fe, Ni, Cu, Zn, Br, I, Sr, Zr, Ag, Cd, Sn, Sb, Xe, Rn, Cs, Ba, Pt, Au, Hg, Pb, W, Fr, Ra, U, Pu (For Monday)

4.1 Studying Atoms

Wrap: 8/24/2011 Pg 102-114

1. Who discovered the nucleus? How? Why did he conclude the nucleus had an overall + charge?

2. Explain how Thomson knew the particles inside the cathode rays were negative.

3. How does the volume of the nucleus compare to the volume of the atom?

4. Write out the actual mass of a proton, neutron and electron( Convert from Sci Not). How does the mass of a proton compare to the mass of an electron? Neutron?

4.1 Studying Atoms

Wrap: 8/24/2011 Pg 102-1141. Give 2 facts about Dalton, Rutherford, and Thomson. How

was Democritus theory different than Aristotle’s?

2. Define 4 vocab terms.

3. Read pg 114. Give 2 facts about each paragragh

STUDY!!! Reminder quiz over first 20 elements Friday, quiz over elements given in class Monday.

4.1 Studying Atoms

Wrap: 8/26/2011 Pg 115-121

1. What is the difference between atomic number, atomic mass and mass number? What is Tin’s atomic number and mass?

2. How do you calculate the number of protons, neutrons, and electrons? Calculate the p, n, e’s of Francium.

3. What is an isotope? Give an ex. How is C-12 different than C-14?

4. How many p,n,e’s does Ag-110 have?

4.1 Studying Atoms

Rap: 1/19/2011 pg: 67-741. How was Democritus theory different than Aristotle’s?

2. What does the law of conservation of mass state?

3. What does Dalton’s atomic theory state? What part do you know is wrong?

4. Give 2 important concepts of the modern atomic theory.

5. Who discovered the electron? What was his model called? Why do you think this model is incorrect

6. Give 3 reasons why it is a bad idea to misbehave for the sub. If you were to apologize for your/your classes behavior to the sub and Mrs. Sleep what would you say?

4.1 Studying Atoms

Rap: 1/19/2011 pg 72-76NO TALKING

1. Who discovered the nucleus? How? Why did he conclude the nucleus had an overall + charge?

2. Explain how Thomson knew the particles inside the cathode rays were negative.

3. How does the volume of the nucleus compare to the volume of the atom?

4. What is located inside the nucleus? Why does it not split apart?

5. What did you learn Yesterday about being bad for a sub when Mr. Campbell is Absent?

4.1 Studying Atoms

RAP: 1/21/2011 Pg: 67-75

1. Give 2 facts about Dalton, Rutherford, and Thomson

2. What is the difference between the law of definite proportion and law of multiple proportions?

2H2 + O2 2 H2O

3. If you have 10g of hydrogen and you add it to 4g of Oxygen how much H2O would you have? What law does this demonstrate?

4.1 Studying Atoms Section 1 The Atom: From Philosophical Idea to Scientific Theory

Foundations of Atoms• Law of definite proportions: a chemical compound

contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound

• Law of multiple proportions: if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

Chapter 3

4.1 Studying Atoms

Law of Multiple ProportionsSection 1 The Atom: From Philosophical Idea to Scientific TheoryChapter 3

4.1 Studying Atoms

Studying the structure of atoms is a little like studying wind. Because you cannot see air, you must use indirect evidence to tell the direction of the wind. Atoms pose a similar problem because they are extremely small. Even with a microscope, scientists cannot see the structure of an atom.

4.1 Studying Atoms

The philosopher Democritus believed that all matter consisted of extremely small particles that could not be divided. He called these particles atoms from the Greek word atomos, which means

“uncut” or “indivisible.”

Ancient Greek Models of Atoms

4.1 Studying Atoms

Aristotle thought that all substances were made of only four elements—earth, air, fire, and water. He did not think there was a limit to the division of matter. For many centuries, most people accepted Aristotle’s views on the structure of matter. By the 1800s, scientists had enough experimental data to support an atomic model.

Ancient Greek Models of Atoms

4.1 Studying Atoms

When magnesium burns, it combines with oxygen. In magnesium oxide, the ratio of the mass of magnesium to the mass of oxygen is always about 3 : 2. Magnesium dioxide has a fixed composition.

What happens if you put water on burning Mg?

Dalton’s Atomic Theory

4.1 Studying Atoms

Magnesium burning

• http://www.youtube.com/watch?v=qrjYb1Oy-Pc

4.1 Studying Atoms

Dalton’s Theory• All elements are composed of atoms.• All atoms of the same element have the

same mass, and atoms of different elements have different masses.

• Compounds contain atoms of more than one element.

• In a particular compound, atoms of • different elements always combine in the

same way.

Dalton’s Atomic Theory

4.1 Studying Atoms

When some materials are rubbed, they gain the ability to attract or repel other materials. Such materials are said to have either a positive or a negative electric charge.

• Objects with like charges repel, or push apart. • Objects with opposite charges attract, or pull

together.

Thomson’s Model of the Atom

4.1 Studying Atoms

Thomson’s Experiments

In his experiments, Joseph John Thomson used a sealed tube containing a very small amount of gas.


Sealed tube filled with gas at low pressure

Glowing beam

Metal disk Source of electric current

Metal disk

Metal disk Source of electric current

Positive plate

Negative plate

4.1 Studying Atoms

When the current was turned on, the disks became charged, and a glowing beam appeared in the tube.

• Thomson hypothesized that the beam was a stream of charged particles that interacted with the air in the tube and caused the air to glow.

• Thomson observed that the beam was repelled by the negatively charged plate and attracted by the positively charged plate.


4.1 Studying Atoms

Evidence for Subatomic Particles

Thomson concluded that the particles in the beam had a negative charge because they were attracted to the positive plate. He hypothesized that the particles came from inside atoms because

• no matter what metal Thomson used for the disk, the particles produced were identical.

• the particles had about 1/2000 the mass of a hydrogen atom, the lightest atom.


4.1 Studying Atoms

• http://www.youtube.com/watch?v=O9Goyscbazk

4.1 Studying Atoms

Thomson’s model is called the “plum pudding” model. Today, it might be called the “chocolate chip ice cream” model.

The chips represent negatively charged particles, which are spread evenly through a mass of positively charged matter—the vanilla ice cream.


4.1 Studying Atoms

What contributions did Rutherford make to the development of atomic theory?

Rutherford’s Atomic Theory

According to Rutherford’s model, all of an atom’s positive charge is concentrated in its nucleus.

4.1 Studying Atoms

Rutherford’s Hypothesis

Ernest Rutherford designed an experiment to find out what happens to alpha particles when they pass through a thin sheet of gold. Alpha particles are fast-moving, positively charged particles.

• Based on Thomson’s model, Rutherford hypothesized that the mass and charge at any location in the gold would be too small to change the path of an alpha particle.

• He predicted that most particles would travel in a straight path from their source to a screen that lit up when struck.


4.1 Studying Atoms

The Gold Foil Experiment


Beam of alpha particles

Source of alpha particles

Slit

Deflected particle

Undeflected particle

Screen

Gold atoms

Alpha particles

Alpha particles

Nucleus

4.1 Studying Atoms

• http://www.youtube.com/watch?v=5pZj0u_XMbc

4.1 Studying Atoms

Discovery of the Nucleus

The alpha particles whose paths were deflected must have come close to another charged object. The closer they came, the greater the deflection.

However, many alpha particles passed through the gold without being deflected. These particles did not pass close to a charged object.


4.1 Studying Atoms

Thomson’s model did not explain all of the evidence from Rutherford's experiment. Rutherford proposed a new model.

• The positive charge of an atom is not evenly spread throughout the atom.

• Positive charge is concentrated in a very small, central area.

• The nucleus of the atom is a dense, positively charged mass located in the center of the atom.


4.1 Studying Atoms

• http://www.youtube.com/watch?v=L2KmCTst2o0&NR=1

4.1 Studying Atoms

The Houston Astrodome occupies more than nine acres and seats 60,000 people. If the stadium were a model for an atom, a marble could represent its nucleus. The total volume of an atom is about a trillion (1012) times the volume of its nucleus.


4.1 Studying Atoms

Assessment Questions

1. Dalton’s theory did not include which of the following points? a. All elements are composed of atoms.

b. Most of an atom’s mass is in its nucleus.

c. Compounds contain atoms of more than one element.

d. In a specific compound, atoms of different elements always combine in the same way.

4.1 Studying Atoms


1. Dalton’s theory did not include which of the following points? a. All elements are composed of atoms.

b. Most of an atom’s mass is in its nucleus.

c. Compounds contain atoms of more than one element.

d. In a specific compound, atoms of different elements always combine in the same way.

ANS: B

4.1 Studying Atoms


2. J. J. Thomson’s experiments provided the first evidence of a. atoms.b. a nucleus.c. subatomic particles.d. elements.

4.1 Studying Atoms


2. J. J. Thomson’s experiments provided the first evidence of a. atoms.b. a nucleus.c. subatomic particles.d. elements.

ANS: C

4.1 Studying Atoms


1. The concept of an atom as a small particle of matter that cannot be divided was proposed by the ancient Greek philosopher, Democritus.

TrueFalse

4.1 Studying Atoms


1. The concept of an atom as a small particle of matter that cannot be divided was proposed by the ancient Greek philosopher, Democritus.

TrueFalse

ANS: T

4.1 Studying Atoms

Notes:• Dalton proposed the theory that all matter is made up of

individual particles called atoms, which cannot be divided.• An atom is neutrally charged unless the atom has lost or

gained electrons• Rutherford found that when he shot a beam of alpha

particles (+) through gold foil some bounced back while some went through

• According to Rutherford’s model, all of an atom’s positive charge is concentrated in its nucleus.


4.1 Studying Atoms

Notes:• Dalton proposed the theory that all matter is made up of

individual particles called atoms, which cannot be divided.

• An atom is neutrally charged unless the atom has lost or gained electrons

• According to Rutherford’s model, all of an atom’s positive charge is concentrated in its nucleus.


4.1 Studying Atoms

Elements to know by Friday Flash Cards?

• First 20 elements name and chemical symbol (H- Ca) (For Friday). Also Atomic Theory

• Also Cr, Fe, Ni, Cu, Zn, Br, I, Sr, Zr, Ag, Cd, Sn, Sb, Xe, Rn, Cs, Ba, Pt, Au, Hg, Pb, W, Fr, Ra, U, Pu (For Monday)

4.1 Studying Atoms

Quiz Tomorrow

• Quiz will be over Chapter 3 sec 1+2

• Look over openers from yesterday and Today.

• Look over notes from Today.

• Make sure you know the table we just did

• Quiz will be 10-15 Q’s long

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Ch4 s1