Chapter 6 The Periodic Table Ms. Wang Lawndale High School

Section 6.1 - Organizing the Elements By the 1700’s, only about 13 elements had been identifies Chemists used the properties of elements to sort them into groups In 1829, J.W. Dobereiner published a classification system with elements grouped into set of three based upon similar chemical properties

Mendeleev’s Periodic Table From 1829 to 1869, many different systems were proposed, but none gained wide acceptance In 1869, Dmitri Mendeleev arranged the elements in his periodic table in order of increasing atomic mass, based upon repeating properties

The Periodic Law In the modern periodic table, elements are arranged in order of increasing atomic number Periodic Law – when elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties

Metals, Metalloids and Nonmetals (Red ladder on the periodic table) Elements can be grouped into three broad classes based on their general properties Metals Nonmetals Metalloids

Metals: elements that are generally solid at room temperature, have a grayish color and shiny surface, and conduct heat and electricity Nonmetals: elements that have varying properties but are generally poor conductors of heat and electricity Metalloids: elements with some properties of metals and and nonmetals

Section 6.2 - Classifying the Elements (Page 162-163) The periodic table displays the symbols and names of the elements, along with information about the structure of their atoms Element symbols that are printed in black are solid at R.T., blue are liquid at R.T., and red are gasses at R.T. Some elements are printed in green, which means that they are not found in nature

The 7 Groups of the Periodic Table Alkali Metals (Group 1A) Alkaline Earth Metals (Group 2A) Chalcogens (Group 6A) Halogens (Group 7A) Noble Gases (Group 8A) Transition Metals (Group B) Inner Transition Metals (Lanthanides and Actinides)

Electron Configurations in Groups Elements can be sorted into noble gases, representative elements, transition metals, or inner transition meals based on their electron configuration Noble Gases always have their s and p sublevels completely filled with electrons, which makes them relatively inactive

Representative Elements Representative Elements are Groups 1A through 7A because they display a wide range of physical and chemical properties For any representative element, its group number always equals the number of electrons in the highest occupied energy level (Valence Shell)

Transition Metals Transition Metals are characterized by the presence of electrons in the d orbital Inner Transition Metals are characterized by the presence of electrons in the f orbital

Section 6.3 – Periodic Trends Properties of elements are related to the location of elements in the periodic table Four periodic trends: Atomic Radius Ionization Energy Electron Affinity Electronegativity

1. Atomic Radius One-half of the distance from center to center of two atoms of the same element Atomic Radius

1. Atomic Radius What do you notice about the atomic radii of the elements on the periodic table?

Atomic Radius Practice Which element has a greater atomic radius? F or Cs Ga or K Kr or Rb Put these elements in order of increasing atomic radius Ba, Si, Fr, W, O, Ag

Ions Remember that atoms that are electrically neutral have equal number of protons and electrons Some compounds are composed of particles called ions. Ions are atoms that have a positive or negative charge.

Ions Positive and negative ions form when electrons are transferred between atoms Cation – an ion with a positive charge Anion – an ion with a negative charge

2. Ionization Energy The energy required to remove an electron from an atom - + Lithium Ion Lithium atom

2. Ionization Energy Elements with low ionization energy are good conductors of electricity

2. Ionization Energy What trend do you notice about the ionization energy of the elements on the periodic table?

Ionization Energy Practice Which of these elements has a greater ionization energy? Ar or Kr Al or Na S or Rb Put these elements in order of increasing ionization energy Si, Cs, He, Ca, P, O

Ionic Size Cations are always smaller than the atoms from which they form Anions are always larger than the atoms from which they form WHY? (Hint: think about the electron cloud of an atom) Which is larger? Na or Na+, Al or Al3+, I or I-, S or S2-

3. Electron Affinity What trend do you notice about the electron affinity of the elements on the periodic table?

4. Electronegativity The tendency of an atom to attract electrons to itself when in a compound

4. Electronegativity What trend do you notice about the electronegativity of the elements on the periodic table?

Electronegativity Practice Which element has greater electronegativity? Na or F Ca or C Al or Mg Put these elements in order of increasing electronegativity Sr, Al, Ca, K, Cl, F

Chapter 6 Assessment (Page 181) Homework Chapter 6 Assessment (Page 181) #’s 26-46, 48, 49, 52, 64