The Periodic Table!  UNIT 6-2 NOTES

I. The Periodic Table of Elements Periodic is a word that describes something that occurs or repeats at regular intervals. The Periodic Table was used to keep track of the different elements that are natural & man made. Developed by Dmitri Medeleev. Mendeleev used atomic mass to organize the elements. The modern (today’s) Periodic Table uses atomic number. Periodic Law is the law that states that the repeating chemical and physical properties of elements change periodically with the atomic numbers of the elements. How elements look and react will be determined by their atomic number.

II.Parts to Know: Atomic Number: tells us number of protons in an atom. The number of protons and the number of electrons in an atom are always the same. This is because we always assume that atoms are neutral. The atomic number is specific to each element, like our DNA or fingerprints. We can change the number, but doing so changes the element we have! Proton = (+) charge Electron = (-) charge +6 plus -6 = 0 0 means neutral charge overall

…more parts… e. Chemical Symbol: letters that are used to represent the names of different elements. f.The first letter is always upper case and the second letter is always lower case. Ex: Chlorine is always Cl. Mass # Symbol Atomic # Order of electrons Al the symbol for Aluminum. Its atomic # is 13. This means it has 13 protons. Its mass is 27.

III. Energy Levels/Shells All atoms have different energy levels. Each energy level/shell can hold a different amount of electrons. For elements 1-20: -2 electrons can fit in the 1st energy level -8 electrons can fit in the 2nd energy level -8 electrons can fit in the 3rd energy level -8 electrons can fit in the 3rd energy level The numbers on the periodic table that are separated with a dash represent the amount of energy levels and the number of electrons in each energy level. This is called the electron configuration (arrangement).

This is the electron configuration. IV.Review… There are 3 shells. There are 2 electrons in the first shell. There are 8 electrons in the second shell. There are 3 electrons in the third shell. This is the electron configuration. 13 P 14 N

V.Valence Electrons Valence electrons are the electrons located in the LAST energy shell of an atom. It is important because it determines how it reacts with other atoms. 11

Example: Valence Electrons # Shells How many valence electrons 2 2 3 3 3 3 1 2 5 6 7 8

There are 7 valence electrons VI.Review of Each “Box” Three shells: 1st shell has 2 electrons 2nd shell has 8 electrons 3rd shell has 7 electrons There are 7 valence electrons Mass # Symbol Atomic # Order of electrons # Protons = 17 # Electrons = 17 # Neutrons = 35 – 17 = 18 11 p 12 n

# of protons = atomic number VII.Organization The elements are arranged by increasing atomic number! (They count up in order!) Remember atomic number is the same thing as the number of protons. The layout of the table (where things are located) is important; the position of things tells us information about specific elements. # of protons = atomic number

VIII.Families/Groups There are columns (vertical) on the periodic table called families. Each family is named and they tell us the number of valence electrons an atom has. Just like our families, elements in the same family have a lot in common. Elements in the Family/Group 17 are used as cleaning products.

Rings = shells = energy levels IX.Periods/Rows There are 7 rows on the periodic table, they tell us the number of shells an atom has. Rings = shells = energy levels (all synonyms)

Row is the same thing as period number! Period/Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Row 7

X.Metals Metals make up most of the Periodic Table. They are on the LEFT of the staircase (zigzag line). Properties of metals: Malleable (can be hammered). Ductile (can be drawn into a wire). Has luster (shiny). Good conductors of heat and electricity.

XI.Nonmetals Nonmetals are located to the RIGHT of the staircase (zigzag line). Properties of nonmetals: Dull Poor conductors of heat and electricity A lot of nonmetals are gasses at room temperature NOT malleable and NOT ductile Brittle (easily smashed into a powder) SULFUR

XII.Metalloids Metalloids are in between metals and nonmetals and are ON the staircase (zigzag line). Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), and Tellurium (Te) Properties of metalloids: They are semiconductors. They have some properties of metals. They have some properties of nonmetals. Ex: Te is shiny AND brittle. Antimony

XIII.Families/Groups

Family/Group 1 These are called the Alkali Metals. Highly reactive, shiny, color of silver, and very soft. Since they are in Group 1, they have 1 valence electron.

Family 2 These are called the Alkaline Earth Metals. Since they are in Family 2, they have 2 valence electrons. They are reactive metals, the color of silver, and are denser than group 1.

Transition Metals Families 3-12 are transition metals because they are transitioning from metals to nonmetals. Their valence electrons vary They are usually very colorful when combined in compounds, like CuSO4.

Families/Groups 13-16 Key: Nonmetals metals metalloids They have metals, nonmetals, and metalloids. They have a different number of valence electrons. Key: Nonmetals metals metalloids

Family 17 These are called the Halogens. They are all nonmetals. They are very reactive and are poor conductors of electricity. They usually combine with group 1 to make salts. F

Family 18 These are called the Noble Gases. They are all nonmetals They are unreactive, colorless, odorless gasses at room temperature.

The Extra 2 Periods/Rows The extra 2 rows are called the Lanthanides and Actinides and are there for a reason! If they were placed where they belong they would push the elements in the respective rows/periods OUT of the correct columns! Also, their placement would put them in Transition Metals; which means their location is more or less irrelevant, while the placement of elements in Groups 13-18 is significant. Lanthanides Actinides