1. Chapter 19 – Properties of Atoms & the Periodic Table
Chapter preview
sections
1 Structure of the Atom
2 Masses of Atoms
3 The Periodic Table
Atoms Compose All Things, Great and Small
Everything in the universe is composed of tiny particles called atoms. You will learn about atoms and their components:
protons, neutrons, electrons, and quarks.

2. Properties of Atoms and the Periodic Table
Section 1—Structure of the Atom
Original Author: Donna Myers

3. Scientific Shorthand Elements are abbreviated in scientific shorthand.
Consist of one capital letter or a capital letter plus one or two small letters.
Some symbols are derived from Latin.
Argentum is Latin for “silver”

4. Learn Table 1 on page 578 Symbols of Some Elements Element Symbol
Aluminum Al
Gold Au
Mercury Hg
Calcium Ca
Helium He
Nitrogen N
Carbon C
Hydrogen H
Oxygen O
Chlorine Cl
Iodine I
Potassium K
Copper Cu
Iron Fe
Silver Ag
Fluorine F
Magnesium Mg
Sodium Na

5. Atom An element is matter that is composed of one type of atom.
Atom is the smallest piece of matter that still has the properties of the element.
A chemical symbol represents the name of an element.

6. Atomic Components Protons—particles with electrical charge of 1+
Neutrons—neutral particles with no electrical charge.
Electrons—particles with electrical charge of 1–
Nucleus—positively charged central core of the atom

7. Atomic components Protons and neutrons are in center of nucleus.
The region around the nucleus occupied by electrons is called the electron cloud.

8. Quarks
The nucleus of the atom contains protons and neutrons that are composed of particles of matter called quarks.
Six quarks are known to exist.
Quarks are studied by colliding accelerated charged particles with protons, which leave tracks in a bubble chamber.
Bubble chamber image
Bubble chamber

9. Tevatron
A tevatron is used to accelerate protons in the study of subatomic particles.

10. Models Scientists use scale-up models to represent atoms.
John Dalton’s atomic model was a simple sphere.

11. Democritis’s Uncuttable Atom
NATIONAL GEOGRAPHIC
Visualizing the Atomic Model
The ancient Greek philosopher Democritis proposed that elements consist of tiny, solid particles that cannot be subdivided.
Democritis’s Uncuttable Atom
Thompson Model, 1904
Rutherford Model, 1911
Bohr Model, 1913
See Figure 5, page 582

12. The Electron Cloud Model (Current)
In 1926, scientists developed the electron cloud model of the atom that is used today.
This model shows electrons traveling in specific energy levels around a nucleus of protons and neutrons.
According to present atomic theory, the location of an electron in an atom cannot be pinpointed exactly.

13. Masses of Atoms
Section 2

14. Atomic Mass Composed mostly of protons and neutrons.
Majority of the mass of an atom is located in the nucleus.

15. Atomic Mass Units
Unit of measurement for atomic particles is atomic mass unit (amu) which is one-twelfth the mass of a carbon atom containing six protons and six neutrons.
1 amu = mass of 1 proton or 1 neutron

16. Comparison of Particles in an Atom
Protons and neutrons are about the same size and mass.
Electrons are about 1,836 times smaller than protons and neutrons.

17. Atomic Number
Protons identify the element.

18. The sum of the number of protons and neutrons in an atom
Mass Number
The sum of the number of protons and neutrons in an atom
Protons + neutrons = mass number
A certain atom has 26 protons, 26 electrons, and 30 neutrons. What is its mass number?

19. Mass Numbers of Some Atoms (page 585)
Element
Symbol
Atomic Number
Protons
Neutrons
Mass Number
Average Atomic Mass
Boron B 5 6 11
10.81
Carbon C 12
12.01
Oxygen O 8 16
16.00
Sodium Na 23
22.99
Copper Cu 29 34 63
63.55

20. Isotopes Atoms of the same element with different numbers of neutrons.
Different isotopes have different properties.
Name of element followed by mass number identifies the isotope.
Carbon-12
Carbon-14
Lead-206

21. Isotopes To find number of neutrons:
mass number – atomic number =
number of neutrons
Atoms of boron have mass numbers of 10 or 11. How many neutrons are in a boron atom?
Boron – 5 = 5 neutrons
Boron – 5 = 6 neutrons

22. Average Atomic Mass
The average atomic mass is the weighted-average mass of the mixture of its isotopes.
Average atomic mass is closest to its most abundant isotope.
Four out of five atoms of boron are boron-11 and one out of five is boron-10
Average atomic mass of boron is close to mass of
most abundant isotope, boron-11.

23. Isotopes The average mass is closest to its most abundant isotope
Chlorine’s atomic mass is List two possible isotopes of chlorine.
Cl-35 and Cl-36

24. Work Section 2 Assessment, page 587
1) Use paper and pencil (colored if you have them) to draw the electron cloud model for lithium. Include the correct number of protons and electrons. Include four neutrons in the drawing.
2) Calculate the weighted average of the following quiz scores: 5 students scored 80%; 19 students scored 90%.
Work Section 2 Assessment, page 587

25. The Periodic Table Section 3

26. Periodic Table
The modern day periodic table is a chart showing the classifications of elements according to their properties and increasing atomic numbers.
The p. t. is useful because it shows the relationship among the elements and it can be used to predict similarities and differences among the elements.

27. Dmitri Mendeleev Developed the first periodic table
He arranged the elements by increasing atomic mass and aligned them in columns based on chemical and physical properties.

28. Groups On The Periodic Table
Elements arranged in vertical columns in the periodic table
Elements in a group have similar properties
Elements in a group have the same number of electrons in their outer energy level.
There are 18 groups

29. Energy Levels There are 7 energy levels
Energy level one contains a maximum of 2 electrons
Maximum number of electrons in second energy level is 8.
Each row in the periodic table ends when an outer energy level is filled.

30. Major energy level K L M N O P Q
Maximum number of electrons 2 8 18 32

31. Noble Gases Group 8A on periodic table
A complete and very stable electron arrangement in the outer energy level will contain 8 electrons—this very stable arrangement is characteristic of noble gases.

32. Electron Dot Diagrams
Are used to show how electrons in the outer energy level are bonded when elements combine to form compounds.

33. Periods
Horizontal rows of elements that contain increasing numbers of protons and electrons.
One proton and one electron are added to each element as you go across the periodic table from left to right.

34. Classification of Elements
All elements in yellow squares are metals.
All elements in green squares are nonmetals
All elements in purple squares are metalloids or semimetal.

35. Properties of Metals Most metals exist as solids at room temperature
They are shiny, can be drawn into wires, pounded into sheets, and are good conductors of electricity.
Moving from left to right in a row of the periodic table, metallic properties of atoms decrease.

36. Properties of Nonmetals and Metalloids
Most are gases
Brittle
Poor conductors of heat and electricity
Metalloids
Have some properties of both metals and nonmetals
Chlorine gas
Boron and silicon

37. Elements in the Universe
All elements throughout the universe are the same.
Hydrogen and helium are the building blocks of other naturally occurring elements.
Scientist believe that naturally occurring elements are manufactured within stars.