Periodic Table "...if all the elements are arranged in order of their atomic weights a periodic repetition of properties is obtained." - Mendeleev The modern periodic table has more than 100 elements and organizes the elements by atomic number.

Elements with similar properties are located in the same vertical columns or groups based on the number of valence electrons they have Valence electrons are electrons in the outer most energy level. There are 18 groups.

The horizontal groups are called periods and are arranged by their energy shells.

Categories on the Periodic Table The elements on the periodic table are categorized based on their physical and chemical properties.

Metals: physical properties are that they are shiny in appearance, malleable (flatten into a sheet), ductile (form into wires); One chemical property is that these elements can conduct electricity or have a high melting point

Non-Metals: physical properties are that they these elements tend to be dull in appearance and brittle (break easily and cannot be made into sheets or wire) They have a low conductivity (not able to conduct electricity well).

Metalloids or Semi-Conductors: share properties of both metals and non-metals.

CATEGORIES OF ELEMENTS GROUPS

Characteristics of Groups All the elements in a group have remarkably similar chemical properties such as conductivity (ability to conduct electricity) or reactivity (ability to react with other elements). Some of the groups have been given special names or are called families to distinguish them.

Group or Family Names Group 1 is called alkali metals Group 2 is call alkali earth metals Groups 3-12 are called the transition metals Group 17 are the halogens Group 18 are the noble gases and are basically inert

Number of Valence Electrons per Group (ELECTRONS IN OUTER MOST ENERGY LEVEL) 1 2 3 4 5 6 7 8

Examples of Lewis Structures per Group Group 1: H ∙ or Li ∙ Group 2: ∙ Ca ∙ . Group 13: ∙ B ∙ .. Group 18: :Ne: ¨

ION FORMATION Elements will gain or lose electrons to become stable—fill their outer energy level. The 1st energy level wants 2 electrons to be stable and the others will be stable with 8 electrons. Elements will gain or lose electrons depending on which way the fewest electrons need to move.

For Example: Group 1 elements have 1 valence electron. It is easier to lose one electron than to gain 7 so these elements will give up one electron to form ions with a +1 charge. Group 17 elements have 7 valence electrons. It is easier to gain one electron than to lose 7 so these elements will gain one electron to form ions with a -1 charge.

What charges will Groups 2, 13, 14, 15, 16, 17, and 18 have when these elements form ions?

Fill in the charges for the ions in each group indicated.

Ion Charges per Group Charges: +1 +2 +3 ±4 -3 -2 -1 0

Examples of Ions Positive Ions or Cations: H+, Mg+2, or Al+3 Negative Ions or Anions: P-3, O-2, or Cl-1

Two Types of Bonds Ionic Bonds form by one elements gaining and another one losing electrons. These type of bonds form between a metal and non-metal such as sodium and chlorine. Covalent Bonds form when elements share electrons and these type of bonds are formed between two non-metals such as carbon and oxygen. (Hydrogen is considered a non-metal so it will form covalent bonds such with hydrogen and oxygen to form water.)

IONIC BONDS An element that wants to lose an electrons to become stable will form an ionic bond with an element that want to gain electrons. That is why these type of bonds form between a metal and a non-metal. Sodium has 1 electron to lose and Chlorine would like to gain one electron to become stable. Sodium and Chlorine will form an ionic bond and make NaCl—sodium chloride.

Naming Ionic Bonds When naming ionic bonds, the cation or positively charged ion is always named first. It keeps its element name. The anion or negative ion is always named second. Its element name is changed by dropping the ending of element’s name and adding “ide”. This means that chlorine is changed to chloride like in sodium chloride—NaCl.

Some examples of Ionic Compounds and their names BaCl2 barium chloride CaO calcium oxide Li2O lithium oxide NaF sodium flouride K2 S potassium sulfide MgS magnesium sulfide 2