Chapter 6 The Periodic Table and Periodic Law

History of the Periodic Table’s Development Antoine Levoisier 1790s compiled a list of known elements. 23 elements on the list. Elements included gold, silver and other elements known since prehistoric times.

History of the Periodic Table’s Development Knowledge explosion due to advances in scientific technology Electricity allowed scientists to break down compounds into their basic elements Spectrometer was used to identify newly isolated elements Industrial Revolution Many new chemistry-based industries (petrochemicals, soaps, dyes, etc.) 1860s - 1870s Chemists agreed to use the Atomic Masses were standardize Over 70 Elements Known

History of the Periodic Table’s Development John Newlands Developed the law of octaves Every 8 elements, the properties repeat Called a period Based on atomic mass Other scientists thought the naming of “Law of Octaves” to be unscientific as it was based on music Meyer Mendeleev Moseley

History of the Periodic Table’s Development, Cont. Meyer, Mendeleev and Moseley Meyer and Mendeleev Understood the correlation between atomic masses and elemental properties Mendeleev organized the first periodic table Left blank spaces where undiscovered elements would go Able to predict properties of yet unknown elements, based on observed trends Periodic Table not Fully Correct

History of the Periodic Table’s Development, Cont. Meyer, Mendeleev and Moseley Moseley Reorganized the periodic table developed by Mendeleev Included newly found elements Discovered each element contains a unique number of elements in their nuclei Rearranged elements by atomic number, not atomic mass Periodic Law: Periodic repetition of chemical and physical properties that are arranged by increasing periodic number

Modern Periodic Table Groups and Periods The Periodic Table will help you organize chemistry knowledge Columns Groups/Families of elements that have similar properties Total 18 Groups Rows Periods of elements that repeat properties Total of 7 periods

Groups and Families Periodic Tables

Modern Periodic Table Classifying Elements 1A) Alkali Metals 2A) Alkaline Earth Metals Both 1A and 2A are chemically Reactive with Alkali being the most reactive of the two 3A) Boron Family 4A) Carbon Family 5A) Nitrogen Family 6A) Oxygen Family 7A) Halogen / Fluorine Family 8A) Noble Gas / Helium Family

Modern Periodic Table Classifying Elements The B Group are the Transition Elements

Groups and Families Periodic Tables

Organizing the Elements by Electron Configuraton Valence Electrons and the Period Valence Electrons and Group/Families Period denotes the highest level energy level Group denotes the number of valence electrons

S, P, D and F Block Elements As S-Orbitals holds maximum of 2 electrons, spans 2 groups P As P-Orbitals hold maximum of 6 electrons, spans 6 groups D Contains transitions metals and is the largest block of elements Characterized by completely filled S orbitals and increasingly filled D orbitals As D-Orbitals hold 10 electrons, spans 10 groups F Contains inner transition metals As F-Orbitals hold 14 electrons, spans 14 groups

Principal Energy Levels The energy level denoted by the principal quantum number n. The first element in a period introduces the new principal energy level. Principal Energy Levels are broken down into sub-levels (S, P, F, D) Period Principal Energy Level Element 1 n = 1 He, H 2 n = 2 Li, Be, B, C, N, O, F, Ne 3 n = 3 Na, Mg, Al, Si, P, S, Cl, Ar 4 n = 4 K, Ca, Ga, Ge, As, Se, Br, Kr 5 n = 5 Rb, Sr, In, Sn, Sb, Te, I, Xe 6 n = 6 Cs, Ba, Ti, Pb, Bi, Po, At, Rn 7 n = 7 Fr, Ra

Bohr Model of the Atom How to Draw a Bohr Model Draw the nucleus. Write element symbol, the number of neutrons and the number of protons in the nucleus. Draw the first energy level. Draw the electrons in the energy levels according to the rules. Make sure you draw the electrons in pairs. Keep track of how many electrons are put in each level and the number of electrons left to use.

Bohr Model of the Atom, Continued Rules for Bohr Energy Levels Level 1: Holds a Maximum of 2e Level 2: Holds a Maximum of 8e Level 3: Holds a Maximum of 8e Level 4: Holds a Maximum of 18e.

Guided Practice on Bohr Models Draw a Bohr Model for C Element Symbol: C Atomic Number: 6 Atomic Mass: 12 Protons: _____________ Neutrons: ______________ Electrons: ______________ Number of Energy Shells: ______________ Number of Valence Electrons (Outer Shell): ____________________________ C

Guided Practice on Bohr Models Draw a Bohr Model for C Element Symbol: C Atomic Number: 6 Atomic Mass: 12 Protons: 6 Neutrons: 6 Electrons: 6 Number of Energy Shells: 2 Number of Valence Electrons (Outer Shell): 4 C Protons: 6 Neutrons: 6

Guided Practice on Bohr Models Draw a Bohr Model for C Element Symbol: C Atomic Number: 6 Atomic Mass: 12 Protons: 6 Neutrons: 6 Electrons: 6 Number of Energy Shells: 2 Number of Valence Electrons (Outer Shell): 4 C Protons: 6 Neutrons: 6

Periodic Trends Atomic Radius Atomic Radius Period Trends: Metals: Atomic radius is half the distance between adjacent nuclei in a crystal of the element Elements that occur as molecules: Half the distance between nuclei of identical atoms that are chemically bonded together. Period Trends: Decrease from Left to Right More valence electrons without higher level orbitals means a higher nuclear charge, condensing the atomic radius Group Trends: Increase from top to bottom Increase in electrons, plus the addition of higher level orbitals.

Periodic Trends

Periodic Trends Ionic Radius Ion: Atom or bonded group of atoms that has either a positive or negative charge They have either gained or lost an electron Ionic Radius: Atomic radius of an ion When ions are formed, it is ALWAYS valence electrons that are either gained or lost When lost (creating a positive CATion), the radius becomes smaller as are either fewer electrons or a completely empty orbital shell When an electron is gained (creating a negative ANion), the radius becomes larger as there are both more electrons and they may be within higher level orbital shells.

Periodic Trends Ionic Radius Period Trends: Group Trends: Increase from Left to Right Left-side of the table form smaller positive ion (CATions) Right-side of the table form larger negative ions (ANions) Group Trends: Increase from top to bottom Increase in electrons, plus the addition of higher level orbitals.

Periodic Trends Ionic Radius

Periodic Trends Ionization Energy Ionization Energy: Energy required to remove an electron from a gaseous atom. First Ionization Energy: The energy required to remove the first electron from an atom Period Trends: First ionization energies increase from left to right, due to the increased nuclear charge (more protons = stronger charge) on the valence electrons Group Trends: First ionization energies decrease from top to bottom on groups, due to the valence electrons being further away from the nucleus in higher level shells.

Periodic Trends Octet Rule Remember “Eight is Great” Atoms tend to gain, lose or share electrons in order to get to 8 valence electrons

Periodic Trends Octet Rule and Electron Configuration When gaining or losing an electron (creating Anions and Cations), the electron configuration needs to change If losing an electron: remove it from the top-level orbital first Li = 1S22S1 Li+ = 1S2 If gain an electron: add it to the top level orbital first and if that is full, add the next level orbital F = 1S22S22P5 F- = 1S22S22P6

Periodic Trends Electronegativity Electronegativity: Indicates the relative ability of an element to attract electrons into a chemical bond Period Trends: Increase as you move left-to-right Group Trends: Decrease as you move down a group Lowest Electronegativity Energies in lower left Highest Electronegativity Energies in upper right