1. Pearson Prentice Hall Physical Science: Concepts in Action
Chapter 4

3. Atom An atom is the smallest particle of an element
Element: an element is a substance that cannot be broken down in simpler substances. It is a single type of atom
ATOMS NOT ADAMS
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4. 4.1
Sizing up the Atom
Despite their small size, individual atoms are observable with instruments such as scanning tunneling microscopes.

5. Subatomic Particles Atoms are made up of three subatomic particles.
4.2
Subatomic Particles
Subatomic Particles
Atoms are made up of three subatomic particles.
What are three kinds of subatomic particles?

6. Three kinds of subatomic particles are: electrons, protons, and
4.2
Subatomic Particles
Three kinds of subatomic particles are:
electrons,
protons, and
neutrons.
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7. Electrons are NEGATIVE Protons are POSITIVE
4.2
Subatomic Particles
Protons and Neutrons
Electrons are NEGATIVE
Protons are POSITIVE
Neutrons are NEUTRAL (Not negative)

8. Electrons are NEGATIVE
4.2
Subatomic Particles
Protons and Neutrons
Electrons are NEGATIVE
They are very small and we generally say they have no mass
They are found outside the nucleus (center) of the atom

9. Have mass (1 amu or atomic mass unit)
4.2
Subatomic Particles
Protons and Neutrons
Protons are POSITIVE
Have mass (1 amu or atomic mass unit)
They are found inside the nucleus (center) of the atom

10. Neutrons are NEUTRAL (Not negative)
4.2
Subatomic Particles
Protons and Neutrons
Neutrons are NEUTRAL (Not negative)
Have mass (1 amu or atomic mass unit)
They are found inside the nucleus (center) of the atom

11. 4.2
Subatomic Particles
Table 4.1 summarizes the properties of electrons, protons, and neutrons.

12. 4.2
The Atomic Nucleus
The Atomic Nucleus: How can you describe the structure of the nuclear atom?
In the nuclear atom, the protons and neutrons are located in the nucleus.
The electrons are distributed around the nucleus and occupy almost all the volume of the atom.
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13. 4.3
Atomic Number
Elements are different because they contain different numbers of protons.
The atomic number of an element is the number of protons in the nucleus of an atom of that element.

14. 4.3
Atomic Number

15. Mass Number How do you find the number of neutrons in an atom?
4.3
Mass Number
Mass Number
How do you find the number of neutrons in an atom?

16. 4.3
Mass Number
The total number of protons and neutrons in an atom is called the mass number.
The number of neutrons in an atom is the difference between the mass number and atomic number.

17. Au is the chemical symbol for gold.
4.3
Mass Number
Au is the chemical symbol for gold.
Au is the chemical symbol for gold. Applying Concepts How many electrons does a gold atom have?

18. for Sample Problem 4.1
Problem Solving 4.17 Solve Problem 17 with the help of an interactive guided tutorial.

19. 4.3
Isotopes
Isotopes
How do isotopes of an element differ?

20. 4.3
Isotopes
Isotopes are atoms that have the same number of protons but different numbers of neutrons.
Because isotopes of an element have different numbers of neutrons, they also have different mass numbers.

21. 4.3
Isotopes
Despite these differences, isotopes are chemically alike because they have identical numbers of protons and electrons.
Neon-20, neon-21, and neon-22 are three isotopes of neon, a gaseous element used in lighted signs. Comparing and Contrasting How are these isotopes different? How are they similar?

22. Atomic Mass How do you calculate the atomic mass of an element?
4.3
Atomic Mass
Atomic Mass
How do you calculate the atomic mass of an element?

23. 4.3
Atomic Mass
It is useful to to compare the relative masses of atoms to a standard reference isotope. Carbon- 12 is the standard reference isotope. Cabon-12 has a mass of exactly 12 atomic mass units.
An atomic mass unit (amu) is defined as one twelfth of the mass of a carbon-12 atom.

24. 4.3
Atomic Mass
The atomic mass of an element is a weighted average mass of the atoms in a naturally occurring sample of the element.
A weighted average mass reflects both the mass and the relative abundance of the isotopes as they occur in nature.

25. 4.3
Atomic Mass
To calculate the atomic mass of an element, multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products.

26. For example, carbon has two stable isotopes:
4.3
Atomic Mass
For example, carbon has two stable isotopes:
Carbon-12, which has a natural abundance of %, and
Carbon-13, which has a natural abundance of 1.11%.

27. 4.2

28. Mendeleev’s Organization
Mendeleev arranged the elements in order of increasing mass
Elements with similar properties were in the same column by using this arrangement
Definition: a periodic table is an arrangement of elements in columns based on a set of properties that repeat from row to row

29. Evidence for the Mendeleev Table
Mendeleev used his organization of the table to predict where undiscovered elements would fit
He deliberately left spaces or gaps in the table for these elements
As new elements were discovered, Mendeleev’s prediction proved to be correct
The close match between the predictions and the actual properties of new elements showed how useful his periodic table could be

30. 5.2 The Modern Periodic Table
Objectives:
1. Describe how the modern periodic table is organized
2. Explain what atomic mass of an element depends on
3. Compare the categories that are used to classify elements on the periodic table
4. Distinguish how properties vary across a period in the periodic table

31. Organization of the Modern Periodic Table
In the modern periodic table, elements are arranged by increasing atomic number
Atomic number is the number of protons
Each ROW of the table is a PERIOD
Each COLUMN is a GROUP or FAMILY
Properties of elements repeat predictably when atomic numbers are used to arrange elements in groups
Definition: periodic law is the predictable pattern of repeating properties in the periodic table

32. Each proton and each neutron weighs one gram
Atomic Mass
Atomic mass is a value that depends in the distribution of an element’s isotopes in nature and the masses of those isotopes
Definition: an atomic mass unit (amu) is one twelfth the mass of a carbon-12 atom
Mass is given in grams
Scientists assigned 12 atomic mass units (amu) or 12 g to the carbon-12 atom which has 6 protons and 6 neutrons
Each proton and each neutron weighs one gram
Electron mass is small and is ignored under this system

33. Definition: an isotope of an element has a different number of neutrons in its nucleus
Since mass is given by protons plus neutrons, isotopes of an element have different masses
It is still the same the element, however, because the number of PROTONS remains unchanged
The number of protons determines which element you have

34. Most elements exist as a mixture of two or more isotopes
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Atomic mass is determined by the weighted average of all the isotopes
The weighted average takes into account how often the isotope occurs by using percentages
The more often an isotope occurs, the more it contributes to the final atomic mass calculation

35. 3 Categories to Classify Elements
Elements are classified as metals, nonmetals and metalloids
Metalloids are also called semiconductors
Metals are good conductors, ductile (can be drawn into wires), malleable, shiny, & solid (with the exception of mercury)
Transition metals (flat part of the table) tend to form compounds with color
Nonmetals are poor conductors, have low boiling points & tend to be gases
Metalloids or semiconductors have properties of both metals & nonmetals

36. How Properties Vary Across the Table
Periods are the rows
Across a period from left to right, the elements become less metallic and more nonmetallic

37. 5.3 Representative Groups
Objectives:
1. Explain why elements in a group have similar properties
2. Describe some properties of the Group A (representative) elements

38. Similar Properties in a Group
Definition: a valence electron is an electron that is in the highest occupied energy level of an atom
Valence electrons are the electrons in the “outer shell”
Elements in a group have similar properties because they have the same number of valence electrons
Elements seek to have complete outer shells with 8 electrons
Therefore, the number of valence electrons determines how reactive the element is

39. Group A Group 1A are the alkali metals
The reactivity of alkali metals increases from the top of Group 1A to the bottom
Group 1A has one valence electron (charge is +1)
Group 2a are the alkaline earth metals
Differences in reactivity among the alkaline earth metals are shown by the ways they react with water: calcium, strontium & barium react easily
These elements have 2 valence electrons (charge is +2)

40. Group 3A is the boron family
Aluminum is in this family & it is the most abundant METAL in earth’s crust
Group 3A has 3 valence electrons (charge is +3)
Group 4A is the carbon family
The carbon family has 4 valence electrons
Except for water, most of the compounds in your body contain carbon
These elements are reactive and will either give up their 4 valence electrons or share 4 valence electrons with other elements (charge is either +4 or -4)

41. The nitrogen family is Group 5A
Group 5A has 5 valence electrons which it can give up (charge +5)
Group 5A can also take in 3 additional electrons from other elements which make a charge of -3
This group is a mixture one metal plus nonmetals & metalloids
The oxygen family is Group 6A
It has both nonmetals & metalloids
Oxygen is most abundant ELEMENT in the earth’s crust
These elements have 6 valence electrons
They seek to acquire 2 more electrons and the family charge is -2 for these elements

42. Group 7A are the halogens
“halo” means salt & “gen” comes from genesis which means beginning or formation
Halogens are salt formers
They readily react with metals
Their 7 valence electrons means they seek one additional electron, giving their family a charge of -1

43. Group 8A are the noble gases
The nobles are colorless, odorless and unreactive because they have 8 valence electrons in their outer shell
Since their outer shell is complete their charge is 0
The nobles are also called the zero elements