The Periodic Table

Early Thoughts Dobereiner – arranged elements with similar chemical properties into triads. Dobereiner – arranged elements with similar chemical properties into triads. Newlands- arranged elements by increasing atomic mass. Came up with groups of 8 called them octaves. Newlands- arranged elements by increasing atomic mass. Came up with groups of 8 called them octaves.

Early Thoughts Mendeleev – Arranged elements by atomic mass Mendeleev – Arranged elements by atomic mass Moseley - discovered each element had a unique positive charge in the nucleus – Atomic number. Moseley - discovered each element had a unique positive charge in the nucleus – Atomic number.

Periodic Law Periodic Law – When elements are arranged in order of increasing atomic numbers, their physical and chemical properties show a periodic pattern. Periodic Law – When elements are arranged in order of increasing atomic numbers, their physical and chemical properties show a periodic pattern.

Terms Groups or families – the vertical columns on the periodic table Groups or families – the vertical columns on the periodic table Periods – The horizontal rows of the periodic table Periods – The horizontal rows of the periodic table Valence Electrons – electrons in the highest principal energy level. Valence Electrons – electrons in the highest principal energy level.

General Trends Periodic Trends-Allow us to see the relationships between the elements and their position on the periodic table Periodic Trends-Allow us to see the relationships between the elements and their position on the periodic table Down a family – more energy levels, more electron shielding. Down a family – more energy levels, more electron shielding. Across a period – same energy level, more protons. Makes the positive nuclear charge greater Across a period – same energy level, more protons. Makes the positive nuclear charge greater

Atomic Radius Atomic Radii- the size from the center of the atom to the outer edge. Atomic Radii- the size from the center of the atom to the outer edge. Period (across the table)-As you go across the table, the atomic radius DECREASES Period (across the table)-As you go across the table, the atomic radius DECREASES Group- As you go down the table, the atomic radius INCREASES. Group- As you go down the table, the atomic radius INCREASES. The largest atomic Radius is Fr The largest atomic Radius is Fr

Ion Size Ion- an atom that has gained or lost one or more electrons “+” ions are smaller than their corresponding atoms “+” ions are smaller than their corresponding atoms “-“ ions are larger than their corresponding atoms “-“ ions are larger than their corresponding atoms Elements in a group form ions of the same charge Elements in a group form ions of the same charge Metals form “+” ions, Metals form “+” ions, Nonmetals form “-“ ions Nonmetals form “-“ ions

Ionization energy Ionization Energy-Tells us how much energy is required to remove one electron from an atom. (measured in joules/mole) Ionization Energy-Tells us how much energy is required to remove one electron from an atom. (measured in joules/mole) A + energy → A+ + e- A + energy → A+ + e- Period-Increase across the period. Period-Increase across the period. Group- decreases as you go down the group. Group- decreases as you go down the group.

Removing multiple electrons. Example, Boron [He] 2s22p1 Example, Boron [He] 2s22p1 IE1 801, IE2 2427, IE3 3660, IE , IE IE1 801, IE2 2427, IE3 3660, IE , IE Where is the big jump in energy and why? Where is the big jump in energy and why? You lose all the valence electrons and are removing core electrons after IE3 You lose all the valence electrons and are removing core electrons after IE3 What has the lowest ionization energy Cs What has the lowest ionization energy Cs

Electron Affinity-The energy change that occurs when an electron is acquired by a neutral atom Most atoms give off energy when an electron is gained Electron Affinity-The energy change that occurs when an electron is acquired by a neutral atom Most atoms give off energy when an electron is gained

Electron Affinity trends Period Trends- as you move across the period, the electron affinity increases until you reach the halogens. Period Trends- as you move across the period, the electron affinity increases until you reach the halogens. Group Trends-As you move down a group, the electron affinity decreases. Group Trends-As you move down a group, the electron affinity decreases. Metals have a low E.A. Metals have a low E.A. Nonmetals have a high E.A. Nonmetals have a high E.A.

Exothermic vs. endothermic F + e- → F- -328KJ/Mole F + e- → F- -328KJ/Mole Exothermic Exothermic Some atoms gain an electron by putting energy into the system. Some atoms gain an electron by putting energy into the system. Mg + e- → Mg- +19KJ/Mole Mg + e- → Mg- +19KJ/Mole Endothermic Endothermic The second type of reaction is very unstable and return to their original state spontaneously. These are usually the noble gases. The second type of reaction is very unstable and return to their original state spontaneously. These are usually the noble gases.

Electronegativity Electronegativity- the ability of an atom in a molecule to attract electrons to itself Electronegativity- the ability of an atom in a molecule to attract electrons to itself Period trend- increases across the period. The metals tend to give electrons away rather than attract them. Period trend- increases across the period. The metals tend to give electrons away rather than attract them. Group Trend- decreases or stays about the same Group Trend- decreases or stays about the same Noble gases aren't electronegative Noble gases aren't electronegative F is the most electronegative element. F is the most electronegative element.