Bell Ringer

Volume Definite Volume

Compressibility Not compressible

Density High

Conductivity Conducts Electricity

Reactivity Very Reactive

Melting Point High

Boiling Point High

Lily is given an unknown substance in class and her teacher has asked her to figure out whether it is a metal or nonmetal. Doing some tests, she discovers some information about the substance:With the information listed in the table what is the substance likely to be, metal or nonmetal? Explain why.

History of Chemistry: Early Greece To Current Day 1

Unit 2 – Atomic Theory

SubUnit - 1

Standard

Explore the scientific theory of atoms by describing the structure of atoms in terms of protons, neutrons, and electrons and differentiate among these particles in terms of their mass, electrical charges and locations within the atom.

Vocabulary

1. atomic mass

2. Law of definite proportions

3. sub-atomic particles

4. alpha particles

5. cathode

6. cathode ray

7. tube

8. theory

Objectives

1. Calculate the atomic mass based on experimental data.

2. Describe the structure of atoms and differentiate among identification, description, location, mass, and electrical charge of atomic particles.

SUBATOMIC PARTICLES

▪Subatomic Particle

▪ A proton is indicated by either the symbol p or p+.

▪The atomic number of an element is the number of protons an atom of that element contains.

▪Protons and neutrons are found in the atomic nucleus, they are collectively known as nucleons.

▪ Inside the Nucleus

▪1.6726219 × 10-27 kilograms

▪Positive Charge

▪ Subatomic Particle

▪ If an atom has equal numbers of electrons and protons, the charges cancel each other out and the atom has a neutral charge.

▪ You could add a thousand neutrons into the mix and the charge would not change.

▪ Deals with creating radioactive atoms.

▪ Neutrons play a major role in the mass and radioactive properties of atoms.

▪ Isotopes are created when you change the normal number of neutrons in an atom.

▪ Inside Nucleus

▪ 1.674929 x 10-27 kg

▪ Neutral Charge

▪ Subatomic Particle

▪ Electrons are extremely small compared to all the other parts of the atom.

▪ The mass of an electron is almost 1,000 times smaller than the mass of a proton.

▪ Electrons are found in clouds that surround the nucleus of an atom.

▪ Generally organized into shells.

▪ Electrons move so quickly; it is impossible to see where they are at a specific moment in time.

▪ Orbiting Nucleus(Outside) in cloud

▪ 9.109390 x 10-31 kg

▪ Negative Charge

ATOMIC MASS

▪Equation For Atomic Mass:

#Protons + #Neutrons = Atomic Mass

▪Atomic Number: #Protons

▪Problems: Tell me the Element & The Atomic Mass

1. 2 Protons & 3 Neutrons

2. 3 Protons & 3 Neutrons

3. 4 Protons & 4 Neutrons

4. 5 Protons & 5 Neutrons

5. 6 Protons & 6 Neutrons

▪ Atomic Mass and Number: https://youtu.be/65dDZulPhtg

▪ Subatomic Particles: https://youtu.be/QRdkQ6SFhQw

Which subatomic particles in an atom contribute to its atomic mass and which of them have little or no impact ?

▪a. Electrons contribute to the atomic mass of an atom while protons and neutrons have little or no impact on the atom's atomic mass.

▪b. Protons and neutrons contribute to the atomic mass of an atom while electrons have little or no impact on the atom's atomic mass.

▪c. Protons and electrons contribute to the atomic mass of an atom while neutrons have little or no impact on the atom's atomic mass.

▪d. Electrons and neutrons contribute to the atomic mass of an atom while protons have little or no impact on the atom's atomic mass.

Which statement below is true?

▪a. The subatomic particles with a negative charge are electrons, those with a positive charge protons and those with no charge neutrons.

▪b. The subatomic particles with a negative charge are electrons, those with a positive charge neutrons and those with no charge protons.

▪c. The subatomic particles with a negative charge are protons, those with a positive charge electrons and those with no charge neutrons.

▪d. The subatomic particles with a negative charge are neutrons, those with a positive charge protons and those with no charge electrons.

1. How many electrons are in the atom in the picture?

a. 1 b. 4 c. 5 d. 3

2. How many neutrons are in the atom in the picture?

a. 1 b. 4 c. 5 d. 3

3. How many protons are in the atom in the picture?

a. 3 b. 5 c. 4 d. 1

4. How many neutrons are in the atom in the picture?

a. 6 b. 5 c. 7 d. 0

5. How many Protons are in the atom in the picture?

a. 5 b. 6 c. 0 d. 1

6. How many electrons are in the atom in the picture?

a. 5 b.7 c.6 d. 0

History of Chemistry: Early Greece To Current Day 2

Unit 2 – Atomic Theory

SubUnit - 1

Standard

1. Describe how scientific inferences are drawn from scientific observations and

provide examples from the content being studied.

2. Explain that scientific knowledge is both durable and robust and open to change.

Scientific knowledge can change because it is often examined and re-examined by

new investigations and scientific argumentation. Because of these frequent

examinations, scientific knowledge becomes stronger, leading to its durability

3. Explain that scientific laws are descriptions of specific relationships under given

conditions in nature, but do not offer explanations for those relationships

4. Describe and explain what characterizes science and its methods.

Objectives

1. Understand the law of definite proportions.

2. Explain that a scientific theory is not established until similar conclusions are yielded by a multitude of experiments conducted by various scientists.

3. Define a scientific law and will identify how observations become a law.

4. Use examples to discuss how similar experiments and investigations conducted in separate locations of the world may either strengthen or weaken a scientific finding.

LAW OF DEFINITE PROPORTIONS❖To make a specific amount of a compound you will

need a specific amount of the reactants.

❖A given chemical compound always contains its component elements in fixed ratio (by mass) and does not depend on its source and method of preparation

Think of baking a cake! The Recipe

is only for 1 cake, but you want to

make 2! So you double everything!

*Changes depending on whose

teaching it or where you are

looking.

Development of a Simple Theory by the Scientific Method:

▪ Observation: Every swan I’ve ever seen is white.

▪ Question: Are all swans white?

▪ Hypothesis: All swans must be white.

▪ Test: A random sampling of swans from each continent where swans are indigenous produces only white swans.

▪ Publication: “My global research has indicated that swans are always white, wherever they are observed.”

▪ Verification: Every swan any other scientist has ever observed in any country has always been white.

▪ Theory: All swans are white.

▪ Prediction: The next swan I see will be white

HYPOTHESIS

1. A reasonable guess based on something that you observe in the natural world.

2. Proven and disproven all the time

3. Foundation of the scientific method.

4. Tested many times by different experts before it is accepted

5. It helps to predict outcomes and define the parameters of the research.

THEORY

▪ Consists of 1+ hypotheses, supported by repeated testing.

▪ Widely accepted in the scientific community as true.

▪ Can evolve. This doesn’t mean the old theory was wrong. It’s just that new information was discovered.

▪ Comprehensive set of ideas explaining a phenomenon in nature.

▪ Allow scientists to make predictions.

▪ One discipline can influence theories in other disciplines.

▪ One theory forms the foundation upon which other theories are built.

▪ Describes how and why something happens.

▪ A theory is an explanation.

▪Describe phenomena, while theories explain why phenomena exist.

▪Short, sweet, and always true.

▪Single statement and generally rely on a concise mathematical equation.

▪Universal and are the cornerstones of science.

▪ If a law were ever to be shown false, any science built on that law would also be wrong.

▪Describe an action under certain circumstances.

▪Tells us that it happens but doesn’t describe how or why.

▪A law is an observation.

THEORY VS. LAW

▪EXAMPLE: Suppose that you were lying under an apple tree and observed an apple fall from a branch to the ground. The observation of this phenomena can be called the law of gravity. The law of gravity states that every time you drop an apple, it will fall to the ground. The theory of gravity is the explanation as to why the apple falls to the ground.

▪ Law Vs Theory: https://youtu.be/GyN2RhbhiEU

▪ Law of Definite Proportions: https://youtu.be/08-96_wkUi8

▪ Scientific Method: https://youtu.be/3nAETHZTObk?t=38

“As galaxies move farther apart from each other, they move faster. A galaxy’s speed is proportional to its distance.” Is this an example of a law or a theory? Support your answer.

How does a theory differ from a law?

History of Chemistry: Early Greece To Current Day 3

Unit 2 – Atomic Theory

SubUnit - 1

Standard

1. Describe the function of models in science and identify the wide range of models used in science.

2. Explore the scientific theory of atoms by describing changes in the atomic model over time and why those changes were necessitated by experimental evidence.

Objectives

• Analyze and differentiate among the theories and associated scientists that led to the modern atomic theory.

• Discuss the importance of certain experiments to the development of atomic theory. For example, cathode ray tube and gold foil experiments led to the discovery of the particles that make up the atom.

• Explain how certain experiments led to the creation of the historical and modern atom models. For example, the plum pudding atom and the nuclear atom were two experiments critical for developing the atomic model.

460BC

1803AD

1897

1911

CATHODE RAY TUBE

▪ J.J. Thomson

▪ Plum Pudding Model

▪ 1897

▪ 3 Different Tubes and Experiments

▪ EXP 1: Bending the rays with a magnet, he could separate the charge from the rays. The negative charge and the cathode rays must somehow be stuck together: you cannot separate the charge from the rays.

▪ EXP 2: Traces of gas remaining in the tube were being turned into an electrical conductor by the cathode rays themselves. To test this idea, he took great pains to extract nearly all the gas from a tube and found that now the cathode rays did bend in an electric field after all.

▪ Conclusion: "I can see no escape from the conclusion that [cathode rays] are charges of negative electricity carried by particles of matter."

▪ EXP 3: Determine the basic properties of the particles. Although he couldn't measure directly the mass or the electric charge of such a particle, he could measure how much the rays were bent by a magnetic field, and how much energy they carried. From this data he could calculate the ratio of the mass of a particle to its electric charge (m/e). He collected data using a variety of tubes and using different gases.

▪ Robert Millikan and Harvey Fletcher

▪ 1909

▪ Measure the elementary electric charge (the charge of the electron).

▪ Before this experiment, existence of subatomic particles was not universally accepted.

▪ Millikan’s apparatus contained an electric field created between a parallel pair of metal plates, which were held apart by insulating material.

▪ Electrically charged oil droplets entered the electric field and were balanced between two plates by altering the field.

▪ When the charged drops fell at a constant rate, the gravitational and electric forces on it were equal. Therefore, the charge on the oil drop was calculated using formula Q= weight/Charge of Electron

▪ Millikan found that the charge of a single electron was 1.6 x 10-19 C. (C= Coulombs)

▪ Ernest Rutherford

▪ Nuclear Model

▪ 1911

▪ Observe the effect of alpha particles on matter

▪ Shot minute particles at a thin sheet of gold.

▪ Small percentage of the particles were deflected, while a majority passed through the sheet.

▪ Concluded that the mass of an atom was concentrated at its center.

▪ Chadwick

▪ Discovered Neutron

▪ 1932

▪ Tightly bound "proton-electron pair"(as Rutherford called it) or neutron(as Chadwick named it)

1913

1926

Current

▪ Atomic Theory: https://youtu.be/thnDxFdkzZs

What evidence is there for the existence of atoms and their sub-atomic particles?