The Periodic Table & Formation of Ions

Development of the Periodic Table Mendeleev: Considered to be the father of the periodic table Arranged elements by increasing atomic mass Placed elements with similar properties in columns Left blank spaces for undiscovered elements Was able to accurately predict properties of the undiscovered elements

The Modern Periodic Table Moseley Arranged elements by increasing atomic number Gave a clearer pattern of periodic properties Periodic Law: there is a periodic repetition of chemical and physical properties of elements when they are arranged by increasing atomic number

Arrangement of the table Groups/Families Columns of elements Numbered 1 to 18 Elements have similar properties Elements have the same # of valence electrons Periods Rows of elements Numbered 1 to 7 Corresponds to number of energy levels of an atom

Groups with Special Names Alkali Metals Group 2: Alkaline Earth Metals Groups 3 -12: Transition Metals Group 17 Halogens Group 18 Noble Gases

Each group contains elements with the same number of valence electrons 1 2 3-12 varies 13 3 14 4 15 5 16 6 17 7 18 8

Example 1 Without drawing electron configurations, determine the number of valence electrons for each of the following: A. Calcium B. Neon C. Sodium D. Aluminum E. Sulfur

Periodic Trends Valence electrons Atomic Radius Ionization Energy: Energy required to remove an electron from a neutral atom Electronegativity: The attraction of an atom for shared electrons in a covalent bond

Atomic Radius Increases from top to bottom in a group Decreases from left to right across a period

Example 2 Arrange each of the following in order of increasing atomic radius (smallest  largest) A. Calcium, Magnesium, Barium B. Fluorine, Iodine, Chlorine C. Calcium, Arsenic, Bromine D. Chlorine, Fluorine, Oxygen

Ionization Energy Increases from left to right across a period Decreases from top to bottom in a group

Example 3 Place the following in order of increasing ionization energy (lowest  highest) A. Sulfur, Oxygen, Selenium B. Calcium, Magnesium, Beryllium C. Lithium, Fluorine, Nitrogen D. Carbon, Silicon, Nitrogen

Electronegatvity Increases from left to right across a period Decreases from top to bottom in a group

Example 4 Determine the most electronegative element in each pair A. Calcium, sulfur B. sulfur, chlorine C. potassium, bromine D. Silicon, phosphorus

Octet Rule Typically, elements want to have 8 valence electrons (except hydrogen and helium) in order to be stable Noble gases are stable because they have 8 valence electrons Other elements will lose, gain, or share electrons in order to have 8 valence

Becoming Stable Remember atoms are neutral because they have equal #’s of protons and electrons When an atom gains or loses electrons, this equality is upset… The atom is no longer neutral…and is no longer called an atom

Ions An ion is an atom that has an electric charge because it has lost or gained electrons If an atom loses electrons, its charge will become positive. It is called a cation. If an atom gains electrons, its charge will become negative. It is called an anion.

On the Periodic Table Group Charge of Ion 1 + 1 2 + 2 3 -12 Varies 13 + 3 14 15 - 3 16 - 2 17 - 1 18 Do not form ions

Ionic Charges The number of electrons that an atom will gain or lose in order to become stable determines its ionic charge Metals lose electrons and have + charge (These are called cations) Nonmetals gain electrons and have – charge (These are called anions)

Size of Ions Cations (+ charges) are smaller than their parent atoms Anions (- charges) are larger than their parent atoms

Example 5 Determine the ionic charge for each of the following. Indicate if it is a cation or an anion: A. Magnesium B. Chlorine C. Oxygen D. Sodium E. Nitrogen

Naming Ions If the ion is positive…name it the atom’s name followed by the word ion Example: Sodium is Na1+…its name is Sodium ion If the ion is negative…change the atom’s name to have an –ide ending then write the word ion Example: Chlorine is Cl1-…its name is chloride ion

Example 6 Indicate the ionic charge and the name of the ion formed from each of the following elements: A. Potassium B. Bromine C. Aluminum D. Cesium E. Fluorine

Element Mg F O K Na Al # Valence electrons Ionic Charge Symbol Name of ion # of protons # of electrons