1. Atoms, Elements and the Periodic Table
Chapter 1

2. STRUCTURE OF MATTER

3. TAKE A DEEP BREATH. What fills your lungs? Can you see it?
Can you hold it in your hand?

4. What is matter? Matter- anything that has mass and takes up space
Is a glass half empty or half full? It’s COMPLETELY full. The rest of the glass is filled with a mixture of gases that make up air.
Even though you can’t see or hold it, air is matter.

5. What isn’t matter? Things that have no mass and do not take up space
Light
Heat
Thoughts
Feelings
Ideas
Reading Check #1

6. What makes up matter? What was Democritus’s idea of matter?
Can matter be made or destroyed?

7. What was Democritus’s idea of matter?
Democritus- a Greek philosopher who lived from about 460 B.C. to 370 B.C.
He thought the universe was made of empty space and tiny bits of “stuff” that he called atoms.
The word atom comes from a Greek word that means “cannot be divided”
Atom- the smallest particle that makes up most types of matter
Reading Check #2

8. Democritus’s Ideas About Atoms
1. All matter is made of atoms.
2. There are empty spaces between atoms.
3. Atoms are complete solids.
4. Atoms do not have anything inside them.
5. Atoms are different in size, shape, and weight.
6. Different types of atoms existed for every type of matter.

9. Can matter be made or destroyed?
People used to think matter disappeared when it burned or rusted.
A French chemist named Lavoisier studied wood fires very carefully.
Wood and the oxygen it combines with during a fire have the same mass as the ash, gases, and water vapor that are produced by the fire.
SO, mass is NOT destroyed, it just changes into a different form.
Reading Check #3

10. Law of Conservation of Matter
From Lavoisier’s work came the law of conservation of matter
Law of Conservation of Matter- matter is not created or destroyed, matter only changes form

11. Models of the Atom What was Dalton’s model of an atom?
How small is an atom?
What is an electron?
What was Thomson’s model of the atom?
What was Rutherford’s model of the atom?
How was the neutron discovered?

12. What was Dalton’s model of an atom?
John Dalton was an English chemist
His model was a set of ideas instead of an object
Believed matter was made of atoms that were too small to see
Thought each type of matter was made of only one kind of atom
Example: Iron atoms made up an iron bar
Dalton’s model became known as the atomic theory of matter
Reading Check #4

13. How small is an atom?
it would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen.
if you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter – about the size of a ping-pong ball
a human hair is about 1 million carbon atoms wide.
a typical human cell contains roughly 1 trillion atoms.
a speck of dust might contain 3x1012 (3 trillion) atoms.
it would take you around 500 years to count the number of atoms in a grain of salt.

14. What is an electron?
English chemist J.J. Thomson discovered the electron in early 1900s
During his experiments, he watched rays travel through a glass tube with a metal plate at each end.
Since the rays could be bent with a magnet, they must be made of particles that had mass and charge.
Electrons- an invisible particle with a negative charge around the nucleus of an atom

15. What was Thomson’s model of an atom?
Thomson thought an atom was made of a ball of positive charge with negatively charged electrons in it.
His model of an atom was like a ball of chocolate chip cookie dough.
The dough was positively charged and the chocolate chips were the negatively charged electrons.
Reading Check #5
Reading Check #6

16. What was Rutherford’s model of an atom?
Scientists still had questions about how the atom was arranged and about particles with positive charge.
Rutherford’s Experiment:
Shot tiny, high-energy, positively charged particles at a thin piece of gold foil
Most particles passed straight through, but others changed direction and bounced back
Because some changed direction, he believed atoms must have positively charged objects within the empty space
He called this the nucleus and the positively charged particles protons
Reading Check #7

17. Rutherford’s Model
Nucleus- the positively charged, central part of an atom
Protons- positively charged particle in the nucleus of an atom

18. How was the neutron discovered?
Rutherford ran into a question:
Why was the nucleus of an atom heavier after his experiment?
Answer: The nucleus was not getting heaver, but the atoms had given off new particles that were not affected by an electric field (neutral).
Neutron- a neutral particle in the nucleus of an atom
Reading Check #8

19. Improving the Atomic Model
Bohr’s Model of an Atom
What is the modern atomic model?

20. Bohr’s Model of an Atom
Scientist named Niels Bohr found that electrons are arranged in energy levels in an atom
The lowest energy is closest to the nucleus
Can only have 2 electrons
Higher energy levels are farther from the nucleus
Can have more than 2 electrons
Electrons were though to orbit, or travel, around the atom’s nucleus

22. What is the modern atomic model?
Electrons have characteristics similar to both waves AND particles
Electrons do not orbit the nucleus of an atom in paths, but move in a cloud around the nucleus.
Reading Check #9

23. + Protons (+) Positively charged particles
Help make up the nucleus of the atom
Help identify the atom (could be considered an atom’s DNA)
Equal to the atomic number of the atom
Contribute to the atomic mass
Equal to the number of electrons + - +

24. Neutrons Neutral particles; have no electric charge+ -
Neutral particles; have no electric charge
Help make up the nucleus of the atom
Contribute to the atomic mass

25. - Electrons (-) Negatively charged particles
Found outside the nucleus of the atom, in the electron orbits/levels; each orbit/level can hold a maximum number of electrons ( 1st = 2, 2nd = 8, 3rd = 8 or 18, etc…)
Move so rapidly around the nucleus that they create an electron cloud
Mass is insignificant when compared to protons and neutrons
Equal to the number of protons
Involved in the formation of chemical bonds + - -

26. Hydrogen (H) Atom - Notice the one electron in the first orbital = 1 +
= 0 -
How many
more electrons
can fit in the 1st
orbital/ level? +
Even though there are no neutrons present,
Hydrogen is still considered an atom

27. Oxygen (O) Atom
Notice the two electrons in the first orbital/level and the six in the second + -
= 8
How many
more electrons
can fit in the 2nd
orbital/ level? - - - + + + + - - + + - - -

28. Sodium (Na) Atom
Notice the two electrons in the first orbital/level, eight in the second, and one in the third + -
= 11
= 12 - - -
How many
more electrons
can fit in the 3rd
orbital/ level? - + + + + - - - + + - - - -

29. + The Atom’s “Center” - - -
Protons and neutrons are grouped together to form the “center” or nucleus of an atom.
Notice that the electrons are not apart of the nucleus + - - -

30. The Simplest Matter

31. The Elements Element- matter mad up of only one kind of atom
Example: gold is made of only gold atoms
At least 118 elements are known
90 elements are found naturally on Earth (oxygen, nitrogen, gold)
Others are synthetic elements, meaning they are created by man (used in smoke detectors and heart pacemaker batteries)
Reading Check #1

32. Early Ideas of Elements
Science has come a long way since Aristotle’s theory of Air, Water, Fire and Earth.
The ancient Greeks believed that there were four elements that everything was made up of: earth, water, air, and fire.

33. The Most Abundant Elements in the Earth’s Crust

34. How would you find a certain book in a library
How would you find a certain book in a library? If you look at the books on the shelves as you walk past, you probably won’t find the book you want. Libraries organize the books to help you quickly find the ones you want. Scientists have organized information about the elements, too. Each element can be found in a chart by their chemical symbol and atomic number.

35. The Periodic Table
The periodic table organizes the elements in a particular way. A great deal of information about an element can be gathered from its position in the period table.
For example, you can predict with the physical and chemical properties of the element and what other elements an element will react with chemically.
Understanding the organization and plan of the periodic table will help you obtain basic information about each of the 118 known elements.

37. How are elements listed in the periodic table?
The table has rows and columns to show how the elements relate to one another.
Rows go from left to right and are called periods
Elements have same number of energy levels
Columns go up and down and are called groups
Elements have similar structural properties G R O U P
PERI D

39. What’s in the square?
Different periodic tables can include various bits of information, but usually:
atomic number
symbol
mass number
number of valence electrons
state of matter at room temperature

40. What is the Atomic Number?
Elements are organized on the table according to their atomic number, usually found near the top of the square.
The atomic number refers to how many protons an atom of that element has.
For instance, hydrogen has 1 proton, so it’s atomic number is 1.
The atomic number is unique to that element. No two elements have the same atomic number.
Reading Check #2
Reading Check #3

41. What would be the atomic number of this atom?
The number of protons in the nucleus of an atom -
What would be the atomic number of this atom? + - -

42. C Cu What is the Symbol? Carbon Copper
All elements have their own unique symbol.
It can consist of a single capital letter, or a capital letter and one or two lower case letters.
Carbon Cu
Copper

43. What is the Mass Number? + +
Mass Number-The total number of protons and neutrons in an atom’s nucleus
Expressed in Atomic Mass Units (amu)
Each proton or neutron has a mass of 1 amu
What would be the mass number of this atom? - +
 3
 4 + -
3 protons + 4 neutrons = a mass number of 7 amu
Why did we not account for the electrons when calculating the mass number? -

44. What is an isotope?
The atomic number is ALWAYS the same for an element, but the number of neutrons in the nucleus can change.
Example: some chlorine atoms have 18 neutrons and some have 20 neutrons
Isotopes- atoms of the same element that have different numbers of neutrons
Isotopes indicate the mass number and atomic mass of an element

45. Mass Number and Isotopes
Mass number changes depending on which isotope is in question
Isotope
Number of Protons
Number of Neutrons
Mass Number
Chlorine-35 17 18 35
Chlorine-37 20 37
Reading Check #4

46. Isotopes of Hydrogen 1 Proton 0 Neutrons Protium 1 Proton 1 Neutron
Deuterium
1 Proton
2 Neutrons
Tritium
Reading Check #5

47. What is atomic mass?
Atomic Mass- the average mass of all the isotopes of an element
This takes into account how OFTEN isotopes are found
The number shown below an element’s chemical symbol is the atomic mass
Example: The mass numbers of the 3 isotopes of hydrogen are 1, 2 and 3. The average of all three when looking at how frequently certain isotopes are found is about

48. Valence Electrons
The number of valence electrons an atom has may also appear in a square.
Valence electrons are the electrons in the outer energy level of an atom.
These are the electrons that are transferred or shared when atoms bond together.

49. Let’s Practice! What is the symbol? What is the name?
What is the atomic mass?
What is the atomic number?

51. Let’s Practice! What is the atomic number? How many protons are there?
How many neutrons are there?
How many electrons are there?

53. Let’s Practice! What is the atomic number? How many protons are there?
How many neutrons are there?
How many electrons are there?
What is the atomic mass?

55. Classification of Elements
The elements are divided into three classes or categories
Metals
Nonmetals
Metalloids
The elements in each category have similar properties

56. Metals
Metals- elements that have a shiny or metallic appearance and are good conductors of heat and electricity
All metals (except mercury) are solids at room temperature
Metals are malleable-they can be bent and pounded into shapes
Metals are ductile-can be stretched into wires without breaking
Examples:
Gold, silver, iron, copper, and lead are examples of metals

57. Metals
Reading Check #6

58. Nonmetals
Nonmetals- elements that usually look dull and are poor conductors of heat and electricity
Brittle-they cannot change shape easily without breaking
Many are gases at room temperature
More than 97 percent of your body is made up of different nonmetals
Examples:
Chlorine, oxygen, hydrogen, nitrogen and carbon

59. Reading Check #7

60. Nonmetals

61. Metalloids
Metalloids- elements that have properties of both metals and nonmetals
All are solids at room temperature
Some are shiny
Many can conduct heat and electricity, but not as well as metals can.
Examples:
Silicon, Arsenic

62. Metalloids

63. Review Metals Nonmetals Metalloids Shiny or metallic
Good conductors of heat and electricity
Almost all are solids
Malleable (bend)
Ductile (stretch)
Dull
Poor conductors of heat and electricity
Many are gases
Brittle (break)
Some are shiny, some are dull
Many can conduct heat and electrcity
All are solids

64. Compounds and Mixtures

65. If you mix together salt and water, what happens to the salt
If you mix together salt and water, what happens to the salt? What happens to the water?

66. Substances
Substance- matter that has the same composition and properties throughout
Scientists classify matter depending on what it is made of and how it behaves
Examples:
Gold
Aluminum

67. What is a Compound?
Compound- substance whose smallest unit is made up of atoms of more than one element bonded together.
Many compounds have properties that are different from those of its elements.
Examples:
Water
Made up of hydrogen and oxygen-both colorless GASES
Hydrogen Peroxide
Made up of hydrogen and oxygen as well

68. What is a Chemical Formula?
Compounds have chemical formulas
A chemical formula shows the elements that make up a compound AND how many atoms of each element are in the compound
When no number is written, it means that the molecule has one atom of that element
Examples:
H2O
2 Hydrogen and 1 Oxygen
H2O2
2 Hydrogen and 2 Oxygen
Reading Check #1
Reading Check #3

70. Are compounds always the same?
A compound is always made of the same elements and in the same proportion
Example:
One unit of water is always made of two hydrogen atoms and one oxygen atom

71. Mixtures
A mixture is made when two or more substances come together but do not combine to make a new substance
The substances can be elements, compounds, or elements and compounds together
The proportions of the substances in a mixture can be changed without changing the identity of the mixture, UNLIKE a compound.
Examples:
Sand and water
Air
Salads

72. How can mixtures be separated?
Solid Mixtures-
Separated by using different screens or filters
Example: Pebbles and Sand
Liquid can be used to separate
Example: If you add water to a mixture of sugar and sand, only the sugar will dissolve in the water. Then, you can pour the mixture through a filter that catches the sand.
Liquid Mixtures-
Boiling can separate a solid from a liquid
Example: Sugar from water

73. What are homogeneous and heterogeneous mixtures?
Homogeneous Mixtures
Heterogeneous Mixtures
Homogeneous- “the same throughout”
Mixtures look the same throughout
May not appear to be a mixture because you can’t see the different parts
Examples: brass, sugar water, and air
Heterogeneous- “completely different”
Have larger parts that are different from each other
You can see the different parts
Examples: Vegetable soup and trail mix
Reading Check #2

74. Compound, Homogeneous Mixture or Heterogeneous Mixture?