# The Periodic Table – Chapter 7

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The Periodic Table – Chapter 7
By Mrs. Shaw

What is the Periodic Table?
Lesson 1: Using the Periodic Table What is the Periodic Table? The Periodic Table is a chart of the elements arranged into rows and columns according to their physical and chemical properties. Columns = Groups Rows = Periods

The Development of the Periodic Table
The Periodic table of elements was devised to organize the known elements into categories that had similar properties. Dimitri Mendeleev, a Russian chemist, decided to organize the elements in order by atomic mass. When he did that he noticed a repeating pattern appeared of elements with similar properties. Periodic means “repeating pattern”. His discovereies happened in 1869 when there were only about 60 elements. His pattern had some gaps though and he theorized that as new elements were discovered they would fill in all the gaps and that is what happened.

Mendeleev’s original periodic table
Notice the gaps that he allowed for.

New discoveries led to new table
In 1914 Henry Moseley, a British scientist, determined that rearranging the elements in order of their atomic number actually worked to align the elements based on their similar physical and chemical properties and filled in all the newly discovered elements. Atomic number = # of protons Element Symbol Element Name Atomic mass (average )

Arranging the Elements
Periods Groups or Families A vertical column of elements is called a group or family. Elements in each group or column usually have similar properties. Each row of elements is called a period.

Periods (rows)-Arranged by increasing atomic weight
Periods have the same number of shells Example: Period 1 = 1 shell Period 2 = 2 shells Period 3 = 3 shells 1 2 3 4 5 6 7 7

Groups- (columns) Arranged by the number of valence electrons
Each group has similar bonding properties Example: Group 1 =1 valence electron Group 2 =2 valence electrons Group 3 = 3 valence electrons 8

Four chemical groups of the periodic table:
alkali metals (IA) alkaline earth metals (IIA), Halogens (VII), Noble gases (VIIIA).

Classification of the Elements
Elements in the periodic table are classified into three main groups: metals, nonmetals, and metalloids.

Over 70% of elements are metals

What are the physical properties of metals?
Metals are elements that are: shiny ductile-easily pulled into wires malleable-hammered into thin sheets good conductors of electricity and thermal energy. Malleable Shiny (have luster) Good conductivity Ductile

Other physical properties of metals
Density, boiling point, and melting points are greater in metals than of other types of elements. AND Except for Mercury all metals are SOLID at room temperature.

Group 1: Alkali Metals Properties Examples
Remember elements in the same group (column) have similar properties. Alkali metals are very reactive (they want to chemically bond so are found in compounds) Pure alkali metals are silvery and soft enough to cut with a knife and have the lowest densities of all metals. Group 1 K + H2O Na

Group 2: Alkaline Earth Metals
Examples Properties React quickly but not as quick as alkali metals. Found as compounds due to their need to react. Soft, silvery with low densities but not as low as alkali metals. Mg

Groups 3-12: Transition Metals
Transition metals have higher densities, boiling points and greater strength than other types of metals (alkali or alkaline earth). They react less than other metals and some exist as free elements (not as a compound). Examples are: Nickel (Ni), Copper (Cu) and Gold (Au)

Nonmetals include the Noble gases.

Properties of Nonmetals
Non-metals are brittle, dull, and not good conductors of thermal or electrical energy. Because they are not good conductors they are really good INSULATORS! Many are gases at room temperature.

Examples of Insulators
The nose cone on the tip of the space shuttles are created using non-metals that insulate against the intense heat of re-entry! Other examples

Lesson 3: Nonmetals and Metalloids
Did you know that more than 96% of your body’s mass comes from just 4 elements – Oxygen, Carbon, Hydrogen, and Nitrogen and all are Nonmetals. Lesson 3: Nonmetals and Metalloids

Metalloids Metalloids have some of the properties of metals and some of the properties of nonmetals. Metalloids

Properties of Metalloids
Metalloids are elements that have properties of both metals and nonmetals. Some metalloids are semiconductors or an element that conducts electricity at a high temperature but not a low temperature

Lanthanide & Actinide Series
Lanthanide series elements are used to make strong magnets. Plutonium is an element in the actinide series that is used as fuel in some nuclear reactors.

Pattern in properties of metals
Metallic properties increase as you move to the left and down on the periodic table.

Valence Electrons Valence electrons are the electrons in the outermost shell that determines a atom’s chemical properties. The amount of electrons in the outer level determine if an atom will likely bond with another – they want to be full so bonding will help that happen.

Chemical bonding Chemical bonding is the joining of atoms to form new substances. A chemical bond is an interaction that holds two atoms together. Most atoms form bonds by gaining, losing, or sharing valence electrons until they fill their outer shell to become “happy”.

Types of Chemical Bonds
There are two types of chemical bonds we will discuss: ionic bonds and covalent bonds.

Ionic Bonds Ionic bonds happen when electrons are transferred from one atom to another, causing the atom to become either positively charged or negatively charged. Na Cl = Na Cl Table Salt

Ionic Bond

Covalent Bonds Covalent bonds happen when atoms share electrons.
For example: Chlorine needs one electron to have a full outer shell so it can share 2 electrons with another Chlorine atom and become stable.

Covalent Bonds Another very important covalent bond is H H O = H2O