Download Chapter 4 - Elements and the Periodic Table I. Introduction to atoms

Chapter 4 - Elements and the Periodic Table
I. Introduction to atoms
A. Development of atomic models
1. Atom, smallest particle of an element
2. Parts of atom
a. Electrons, negatively charged
b. Protons, positively charged
c. Nucleus, center of atom
B. Modern atomic model
1. Includes neutron, electrically neutral in nucleus
2. Number of protons equals number of electrons
3. Protons and neutrons make up mass of atom
4. Measured in atomic mass units (amu)
5. Atomic number
a. Number of protons in nucleus
b. Identifies an element
6. Isotopes
a. Same number of protons and electrons
b. Different number of neutrons
7. Mass number
a. Sum of protons and neutrons in nucleus
b. Identifies isotope
II. Organizing the elements
A. Patterns in the elements
1. Mendeleev (Russian scientist) discovered a set of patterns in elements
2. Arranged elements in order of increasing atomic mass
3. Periodic table contains rows of elements
B. Organization of the periodic table
1. Horizontal rows called periods
2. 18 vertical columns, groups or families
3. Information about element in its square
a. Atomic number
b. Chemical symbol
c. Name
d. Atomic mass
C. How elements form in stars
1. Nuclear fusion
a. Two atomic nuclei fuse together
b. Heavier element is created
2. Energy is released
III. Metals
A. Properties of metals
1. Physical properties
a. Shininess
b. Malleability
c. Ductility
d. Conductivity
2. Chemical properties
a. Reactivity
b. Corrosion
B. Metals in the periodic table
1. Reactivity of elements decreases as you move from left to right
2. Alkali metals, Group 1
a. React by losing an electron
b. Found only as compounds
3. Alkaline earth metals, Group 2
a. React by losing 2 electrons
b. Found only as compounds
c. Good conductors of electricity
4. Transitional metals, Group 4
a. Hard and shiny
b. Good conductors of electricity
c. Form colorful compounds
d. Less reactive than Groups 1 and 2
5. Metals in mixed groups, Groups 13 to 15
a. Few are metals
b. Not nearly as reactive as above groups
6. Lanthanids
a. Soft, malleable, shiny
b. High conductivity
c. Mixed with common metals to make alloy
7. Actinides
a. Only 4 occur naturally on Earth
b. Others created artificially in laboratories
c. Very unstable
8. Synthetic elements
a. Have atomic numbers higher than 92
b. Made in particle accelerators
IV. Non metals and metalloids
A. Properties of nonmetals
1. Physical properties
a. 16 nonmetals are gases at room temperature
b. Dull
c. Brittle
d. Poor conductors of heat and electricity
2. Chemical properties
a. Most are reactive
b. Readily form compounds
c. Fluorine (F) most reactive element
B. Families of nonmetals
1. Carbon family, Group 14
a. Can gain, lose or share 4 electrons
b. Carbon only nonmetals in group
c. Important element for life
2. Nitrogen family, Group 15
a. Contains 2 nonmetals, nitrogen and phosphorus
b. Share 3 electrons
c. Does not react with other elements
d. Occurs as diatomic molecule (N2)
e. Phosphorus more reactive and found as compound
3. Oxygen family, Group 16
a. Contains 3 nonmetals, oxygen, sulfur and selenium
b. Gain or share 2 electrons
c. Oxygen exists as diatomic molecule (O2)
d. Oxygen is highly reactive
4. Halogen family, Group 17
a. Salt forming elements
b. Gains or shares one electron
c. Very reactive
d. Dangerous to humans
e. Many compounds of halogens are useful
5. Noble gases, Group 18
a. Don’t form compounds
b. Very unreactive
c. All exist in Earth’s atmosphere
6. Hydrogen
a. Simplest and smallest atom
b. Has one proton and one electron
c. Most is combined with oxygen (example: H2O)
C. Metalloids
1. Solid at room temperature
2. Brittle
3. Hard
4. Somewhat reactive
5. Have a varying ability to conduct electricity, semiconductor
V. Radioactive elements
A. Radioactivity
1. Unstable isotopes
2. Radioactive decay
a. Fast-moving particles are released
b. Energy is released
3. Discovered in 1896 by French scientist, Henri Becquerel
4. Named by Marie Curie
5. Radioactive minerals
a. Uranium
b. Polonium
c. Radium
B. Types of radioactive decay
1. Alpha decay
2. Beta decay
3. Gamma radiation, accompanies alpha and beta decay
4. Effects of nuclear radiation
a. Alpha particles stopped by sheets of paper
b. Beta particles blocked by aluminum 5 mm thick
c. Gamma rays blocked by lead or concrete wall
C. Using radioactive isotopes
1. Tracers
a. Traces steps of chemical reaction
b. Traces steps of industrial processes
2. Medical uses
a. Diagnosing disease
b. Treating disease