2. Discovering a Pattern
In 1869, Russian chemist Dmitri Mendeleev arranged the elements in order of increasing atomic mass.

3. His Periodic table showed that
Elements with similar properties occurred in a repeating pattern
There were gaps in its pattern
He could predict the properties of the missing elements
By 1886, all of the gaps had been filled and Mendeleev’s predictions were right.

4. Changing the Arrangement
A few elements’ properties did not fit in the pattern of Mendeleev’s table.
1914: British scientist Henry Moseley found the atomic number of atoms.
Elements arranged by atomic number fit the pattern in Mendeleev’s table.

5. Elements are arranged:
Vertically into Groups
Horizontally Into Periods

6. Why?

7. Each group has distinct properties
The periodic Table is divided into several groups based on the properties of different atoms.

8. If you looked at one atom of every element in a group you would see…

9. Each atom has the same number of electrons in it’s outermost shell.
An example…

10. The group 2 atoms all have 2 electrons in their outer shells
Be (Beryllium)
Atom
Mg (Magnesium) Atom

11. Valence electrons
Definition: the number of electrons in the outer shell of an element
Electrons held most loosely
an outer shell is considered complete when it contains 8 electrons
Each element has specific number from 1 to 8
effects the way an atom bonds
Period ends when valence = 8
determines many properties of the element
elements within a group usually have similar properties.

12. One way to represent atoms and molecules is to use electron-dot diagrams. An electron-dot diagram shows only the valence electrons in an atom.

13. If you looked at an atom from each element in a period
you would see…

14. Each atom has the same number of electron holding shells.
An example…

15. The period 4 atoms each have 4 electron containing shells
4th Shell
K (Potassium)
Atom
Kr (Krypton)
Atom
Fe (Iron) Atom

16. The Periodic Table and Classes of Elements
Elements are classified as metals, nonmetals, and metalloids based on number of electrons in outer shell
The zigzag line on the periodic table can help you recognize which elements belong in which category.

17. Metals found to the left of the zigzag line
have few electrons in their outer energy level.
shiny, ductile, malleable, and are good conductors of electric current and thermal energy.

18. Metalloids border the zigzag line
have about half of a complete set of electrons in their outer energy level.
Metalloids have some properties of metals and some properties of nonmetals.
Metalloids are also called semiconductors.

19. Nonmetals to the right of the zigzag line
have an almost complete set of electrons in their outer energy level.
not shiny, ductile, or malleable, and poor conductors of electric current and thermal energy.

20. Group 1: Alkali Metals Alkali metals properties: metals
1 electron in the outer level
very reactive
softness, color of silver, shininess, low density

21. Soft, silvery colored metals
Alkali Metals
Soft, silvery colored metals
Very reactive!!!

22. Alkali Metals reacting with water:
Li (Lithium)
Na (Sodium)
K (Potassium)
Rb (Rubidium)
Cs (Cesium)
What would you expect from Francium?!?!

23. Group 2: Alkaline-Earth Metals
Alkaline-earth metals properties:
metals
2 electrons in the outer level
very reactive, but less reactive than alkali metals
color of silver, higher densities than alkali metals

24. Alkaline Earth Metals
Silvery-White Metals
Fairly reactive
Many are found in rocks in the earth’s crust

25. Group 3–12: Transition Metals
Properties of Transition Metals vary widely but include:
metals
1 or 2 electrons in the outer level
less reactive than alkaline-earth metals
shininess, good conductors of electric current and thermal energy

26. Transition Metals
Most are good Conductors of electricity
Malleable (easily bent/hammered into wires or sheets)

27. How many things can you think of that have Transition Metals in them?

29. Metalloids lie on either side of these “stairsteps”
They share properties with both metals and non-metals
Si (Silicon) and Ge (Germanium) are very important “semi-conductors”

30. What are semiconductors used in?

31. Nonmetals
Brittle
Do not conduct electricity

32. Group 13: Boron Group Group 13 properties:
one metalloid and five metals
3 electrons in the outer level
reactive
solids at room temperature

33. Group 14: Carbon Group Group 14 properties:
one nonmetal, two metalloids, and two metals
4 electrons in the outer level
reactivity varies among the elements
solids at room temperature

34. Group 15: Nitrogen Group Group 15 properties:
two nonmetals, two metalloids, and two metals
5 electrons in the outer level
reactivity varies among the elements
solids at room temperature (except for nitrogen, which is a gas)

35. Group 16: Oxygen Group Group 16 properties:
group contains three nonmetals, one metalloids, and one metal
6 electrons in the outer level
reactive
solids at room temperature (except for oxygen, which is a gas)

36. Halogens
Most are Poisonous
Fairly reactive

37. Chapter 12 Group 17: Halogens
Section 2 Grouping the Elements
Group 17: Halogens
Halogens are the elements in Group 17. Group 17 properties:
group contains nonmetals
7 electrons in the outer level
very reactive
poor conductors of electric current, never in uncombined form in nature

38. Chlorine Gas was used as a chemical weapon during World War I.
It was used by the Nazis in World War II.

39. Chapter 12 Group 18: Noble Gases
Section 2 Grouping the Elements
Group 18: Noble Gases
Noble gases are the elements in Group 18. Group 18 properties:
group contains nonmetals
8 electrons in the outer level (except helium, which has 2)
unreactive
colorless, odorless gases at room temperature

40. Noble Gases
Unreactive
Gases at room temperature

41. Jellyfish lamps made with noble gases artist- Eric Ehlenberger

42. Colors Noble Gases produce in lamp tubes:
Ne (Neon): orange-red
Hg (Mercury): light blue
Ar (Argon): pale lavender
He (Helium): pale peach
Kr (Krypton): pale silver
Xe (Xenon): pale, deep blue

43. Group 3–12: Transition Metals, continued
Lanthanides and Actinides Some transition metals from Periods 6 and 7 appear in two rows at the bottom of the periodic table. Elements in the first row are called lanthanides and elements in the second row are called actinides.

44. Lanthanide Series
Actinide Series

45. Hydrogen
The properties of hydrogen do not match the properties of any single group, so hydrogen is set apart.
a nonmetal
1 electron in the outer level
reactive
colorless, odorless gas at room temperature, low density

46. Section 2 The Atom
Chapter 11
Isotopes
Isotopes are atoms that have the same number of protons but have different numbers of neutrons.

47. Chapter 11 Isotopes, continued
Section 2 The Atom
Chapter 11
Isotopes, continued
Properties of Isotopes An unstable atom is an atom with a nucleus that will change over time. This type of isotope is radioactive.
Telling Isotopes Apart You can identify each isotope of an element by its mass number. The mass number is the sum of the protons and neutrons in an atom.

48. Section 2 The Atom
Chapter 11
Isotopes, continued

49. Naming Isotopes: write the name of the element followed by a hyphen and the mass number of the isotope. Example: Uranium-238
The atomic mass of an element is the weighted average of the masses of all the naturally occurring isotopes of that element.

50. Section 2 The Atom
Chapter 11

51. Chapter 12
The Periodic Tables
Concept Map
Use the terms below to complete the concept map on the next slide.
elements
periods
metals
electrons
nonmetals
periodic table
groups (families)

52. Chapter 12
The Periodic Table

53. Chapter 12
The Periodic Table

54. Chapter 12
Standardized Test Preparation
1. Which of the following statements is correct for the elements shown?
A Lithium has the greatest atomic number.
B Sodium has the least atomic mass.
C Atomic number decreases as you move down the column.
D Atomic mass increases as you move down the column.

55. Chapter 12
Standardized Test Preparation
1. Which of the following statements is correct for the elements shown?
A Lithium has the greatest atomic number.
B Sodium has the least atomic mass.
C Atomic number decreases as you move down the column.
D Atomic mass increases as you move down the column.

56. Chapter 12
Standardized Test Preparation
2. Which of the following statements best describes the outer electrons in atoms of the elements shown?
F The atoms of each element have 1 outer-level electron.
G Lithium atoms have 3 outer-level electrons, sodium atoms have 11, and potassium atoms have 19.
H Lithium atoms have 7 outer-level electrons, sodium atoms have 23, and potassium atoms have 39.
I The atoms of each element have 11 outer-level electrons.

57. Chapter 12
Standardized Test Preparation
2. Which of the following statements best describes the outer electrons in atoms of the elements shown?
F The atoms of each element have 1 outer-level electron.
G Lithium atoms have 3 outer-level electrons, sodium atoms have 11, and potassium atoms have 19.
H Lithium atoms have 7 outer-level electrons, sodium atoms have 23, and potassium atoms have 39.
I The atoms of each element have 11 outer-level electrons.

58. Chapter 12
Standardized Test Preparation
3. The elements featured in the image belong to which of the following groups?
A noble gases
B alkaline-earth metals
C halogens
D alkali metals

59. Chapter 12
Standardized Test Preparation
3. The elements featured in the image belong to which of the following groups?
A noble gases
B alkaline-earth metals
C halogens
D alkali metals

60. Chapter 12
Standardized Test Preparation
2. A chemical company is preparing a shipment of 10 g each of four elements. Each element must be shipped in its own container that is completely filled with the element. Which container will be the largest?
F the container of aluminum
G the container of arsenic
H the container of germanium
I the container of silicon
Element
Density (g/cm3)
Mass (g)
Aluminum
2.702 10
Arsenic
5.727
Germanium
5.350
Silicon
2.420

61. Chapter 12
Standardized Test Preparation
2. A chemical company is preparing a shipment of 10 g each of four elements. Each element must be shipped in its own container that is completely filled with the element. Which container will be the largest?
F the container of aluminum
G the container of arsenic
H the container of germanium
I the container of silicon
Element
Density (g/cm3)
Mass (g)
Aluminum
2.702 10
Arsenic
5.727
Germanium
5.350
Silicon
2.420