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Chapter 5: The Periodic TablePEPSRainier Jr/Sr High SchoolMr. Taylor
Section 1: Organizing the Elements Russian chemist Dmitri Mendeleev in
the 1860’s knew about 60 elements and their atomic masses.
When he placed these elements in order by atomic mass he saw that chemical properties repeated at regular intervals (periodic repetition).
Section 1: Organizing the Elements Mendeleev’s table had gaps in it but he
predicted the properties of these “gap” elements Predictions were close when these
elements were discovered.
Section 1: Organizing the Elements A few elements did not fit the pattern
Henry Moseley (English chemist) rearranged the elements by atomic number; problem solved.
The Periodic Law: when arranged by increasing atomic number, elements have similar chemical properties that repeat at regular intervals (periods).
Section 1: Organizing the Elements
Chemical symbol
Chemical name
Section 1: Organizing the Elements The rows are called periods
Elements become less metallic from left to right
The columns are called groups. Each column (group) has similar chemical
properties
Section 2: Exploring the Periodic Table The periodic repetition of chemical
properties is the result of the arrangement of electrons in the outer energy level (valence electrons).
Variations in physical properties are due to different atomic numbers (protons).
Section 2: Exploring the Periodic Table Elements are place in;
Rows by the number of electron energy levels
Columns by the number of electrons in the outer energy level (valence electrons).
Section 2: Exploring the Periodic Table Ion Formation
Atoms may gain or lose electrons to form ions
Ions are charged particles because they do not have the same number of protons and electrons (unbalanced charges).
Section 2: Exploring the Periodic Table Ion Formation
Atoms gain or lose electrons to achieve a full outer energy level.
Group 1; loses an electron easily, has a positive charge (cation).
Group 17; gain an electron easily, has a negative charge (anion)
Section 2: Exploring the Periodic Table Metals vs non-metals
Metals areShiny solids (mostly)Malleable (able to be hammered into
shapes)Ductile (can be stretched into wires)Conductors of electricity and heat
Section 2: Exploring the Periodic Table Metals vs non-metals
Non-metals areSolids, liquids, or gases at room
temp.Often dull and brittlePoor conductors of heat and
electricity (insulators)
Section 2: Exploring the Periodic Table Metals vs non-metals
SemiconductorsHave some properties of metals and
non-metalsAre used in computer chips
Section 3: Families of Elements Elements of a family have the same
number of valence electrons
Metals: left side of table Non-metals: right side of table
Section 3: Families of Elements Alkali metals: Group 1
One valence electron Form an ion with a 1+ charge HIGHLY reactive
Never found in Nature except combined with another element in a compound
Section 3: Families of Elements Alkaline Earth metals: Group 2
2 valence electrons Form a 2+ ion Very reactive, but less than Group 1
Section 3: Families of Elements Transition Metals
Number of valence electrons varies Some are reactive (iron), some are not
(Gold) Many metals we use everyday are in
this group (Iron, gold, aluminum, copper).
Section 3: Families of Elements Noble gases: Group 18
Full outer valence electron energy level
Non-reactive gases do not usually form compounds or molecules.
Section 3: Families of Elements Halogens: Group 17
7 electrons in outer energy level (almost full).
Gain 1 electron easily to fill the level; 1- charge
VERY reactive; combine easily with metals to form a salt (NaCl, KCl, SnF2).
Section 3: Families of Elements Other non-metals
Oxygen and Nitrogen are the most abundant gases in the atmosphere.
Carbon compounds form the basis of most of the molecules in living organisms.
Section 3: Families of Elements Semiconductors
Also called metalloids Silicon makes up 28% of the matter in
the Earth’s crust Sand is mostly silicon dioxide.