chapter 4: atoms, elements, and the periodic table table of contents section 3: compounds and...

Chapter 4: Atoms, Elements, and the Periodic Table

Table of Contents

Section 3: Compounds and Mixtures

Section 1: Structure of Matter

Section 2: The Simplest Matter

• Matter is anything that has mass and takes up space.

• Even though you can’t see it or hold it in your hand, air is matter.

A.What is matter?I. Structure of Matter

1

• Light and heat do not take up space, and they have no mass. Therefore, they are not forms of matter.

• Emotions, thoughts, and ideas are not matter either.

B. What isn’t matter?Structure of Matter

1

C. What makes up matter?1. An Early Idea -

Structure of Matter

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atom - a small particle that makes up most types of matter.

2. law of conservation of matter - matter is not created or destroyed—it only changes form. From Lavoisier’s work.

• Models are often used for things that are too small or too large to be observed or that are too difficult to be understood easily.

• In the case of atoms, scientists use large models to explain something that is too small to be looked at.

Structure of Matter1

• These models of the atom were used to explain data or facts that were gathered experimentally.

• As a result, these models are also theories.

matter was made of atoms that were too small to be seen by the human eyea set of ideas not a physical objectknown as the “atomic theory of matter”

1. John Dalton’s Atomic Model

Structure of Matter

1 D. Models of the Atom

• No matter what kind of model you use to picture it, the result is the same—an atom is an extremely small particle of matter.

• Atoms are so small it would take about 1 million of them lined up in a row to equal the thickness of a human hair.

2. Sizes of AtomsStructure of Matter

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invisible, negatively charged particles, discovered by J.J. Thomson

3. Discovering the Electron -Structure of Matter

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a solid ball of positive charge with electrons embedded in it

4. Thomson’s ModelStructure of Matter

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5. Rutherford—The Nucleus -Structure of Matter

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the positively charged, central part of the atom .

protons - the positively charged particles in the nucleus

6. Discovering the Neutron -Structure of Matter

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particles that come from the nucleus and have no charge

E. Improving the Atomic ModelStructure of Matter

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• The lowest energy level is closest to the nucleus and can hold only two electrons.

• Early in the twentieth century, a scientist named Niels Bohr found evidence that electrons in atoms are arranged according to energy levels.

• Higher energy levels are farther from the nucleus and can contain more electrons.

Improving the Atomic ModelStructure of Matter

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because electrons have characteristics that are similar to waves and particles, their energy levels are not defined, planet-like orbits around the nucleus. Rather, it seems most likely that electrons move in what is called the atom’s electron cloud.

1. The Modern Atomic ModelStructure of Matter

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Click image to view movie.

• The electron cloud is a spherical cloud of varying density surrounding the nucleus.

2. The Electron CloudStructure of Matter

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• The varying density shows where an electron is more or less likely to be.

The Electron CloudStructure of Matter

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• Atoms with electrons in higher energy levels have electron clouds of different shapes.

• Generally, the electron cloud has a radius 10,000 times that of the nucleus.

1Section Check

Question 1

Anything that has mass and takes up space is an example of _______?

1Section Check

Question 2

Why isn’t a sunbeam an example of matter?

Answer

The answer is matter. Any object you can name—from pine trees to galaxies—is matter.

1Section Check

A sunbeam is made up of light. It doesn’t have any mass, so although it is quite real, it isn’t matter in the scientific sense of the word.

Answer

Question 3

What is the law of the conservation of matter?

1Section Check

The law of the conservation of matter states that matter can neither be created nor destroyed; it only changes forms.

Answer

A.The Elements —One Kind of Atom

• An element is matter made of only one kind of atom.

II. The Simplest Matter2

B. The Periodic Table — 1. Charting the Elements

The Simplest Matter2

• Chemists have created a chart called the periodic table of the elements to help them organize and display the elements.

• Each element is represented by a chemical symbol that contains one to three letters.

• The elements are organized on the periodic table by their properties.

The Periodic Table— Charting the Elements

The Simplest Matter2

The Periodic Table— Charting the Elements

The Simplest Matter2

• The columns are called groups.

• The rows in the table are called periods.

C. Identifying Characteristics

The Simplest Matter2

1. Number of Protons and Neutronsatomic number - top number, tells you the number of protons in the nucleus of each atom of that element.

2. Isotopes -

The Simplest Matter2

atoms of the same element that have different numbers of neutrons.

• An atom’s mass number is the number of protons plus the number of neutrons it contains.

3. Atomic Mass -

The Simplest Matter2

the weighted average mass of the isotopes of an element.

• The atomic mass is the number found below the element symbol.

• The unit that scientists use for atomic mass is called the atomic mass unit, which is given the symbol u.

1. Metals generally have a shiny or metallic luster and are good conductors of heat and electricity. All are solids at room temperature, except mercury.

D. Classification of Elements

The Simplest Matter2

• Elements fall into three general categories — metals, metalloids, and nonmetals.

Classification of Elements

The Simplest Matter2

• Metals are malleable (MAL yuh bul), which means they can be bent and pounded into various shapes.

• Metals are also ductile, which means they can be drawn into wires without breaking.

• Most of the elements are metals.

• Some metalloids are shiny and many are conductors, but they are not as good at conducting heat and electricity as metals are.

The Simplest Matter2

2. Metalloids are elements that have characteristics of metals and nonmetals.

• All metalloids are solids at room temperature.

The Simplest Matter2

3. Nonmetals are elements that are usually dull in appearance.• Most are poor conductors of heat and

electricity. • Many are gases at

room temperature, and bromine is a liquid.

• The solid nonmetals are generally brittle, meaning they break easily.

The Simplest Matter2

• The nonmetals are essential to the chemicals of life.

• More than 97 percent of your body is made up of various nonmetals.

2Section Check

Question 1

What is the term for matter composed of only a single kind of atom?

A. compoundB. elementC. mixtureD. substance

2Section Check

Answer

The correct answer is B. Gold is an example of an element.

2Section Check

Question 2What is the name of the chart, composed by chemists, that arranges all the known elements, their properties, and their symbols?

2Section Check

The chart is known as the periodic table. Answer

2Section Check

Question 3Every atom of the same element has the same number of protons. However, a given atom may have more neutrons than another atom of the same element. Atoms of an element with different numbers of neutrons are known as _______?

2Section Check

Answer

The answer is isotopes. Chlorine-35 and chlorine-37 are examples of isotopes.

A.Substances - matter that has the same composition and properties throughout.

III.Compounds and Mixtures

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1. Compounds -

Compounds and Mixtures

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a substance whose smallest unit is made up of atoms of more than one element bonded together.

B. Mixtures -when two or more substances come together but don’t combine to make a new substance.

Compounds and Mixtures

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• Mixtures can be classified as homogeneous or heterogeneous.

Homogeneous • Homogeneous means “the same throughout.”

Compounds and Mixtures

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• You can’t see the different parts in this type of mixture.

• You might not always know that homogeneous mixtures are mixtures because you can’t tell by looking.

• Homogeneous mixtures can be solids, liquids, or gases.

Heterogeneous

• A heterogeneous mixture has larger parts that are different from each other.

Compounds and Mixtures

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• You can see the different parts of a heterogeneous mixture, such as sand and water.

Section Check

3

A substance whose smallest units are made of atoms of more than one element which have become bonded together is known as a _______?

A. compoundB. double elementC. mixtureD. solution

Question 1

Section Check

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The answer is A. Every time you get in the shower you are covering yourself with a compound: water.

Answer

Question 2How many atoms of hydrogen are signified by the formula 6 H2O?

Section Check

3

The answer is 12. The number 6 tells you there are 6 examples of hydrogen, each of which has two atoms.

Answer

Question 3What do you get when you put together two or more substances but they do NOT combine to form a new substance?

Section Check

3

The answer is a mixture. Right now you are breathing in a mixture. Air is a mixture of oxygen, nitrogen, and some other gases.

Answer

End of Chapter Summary File