CHE 110 Chapter Notes - Chapter 8: Isoelectronicity, Community Reinvestment Act, Electron Affinity
7 May 2018
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Chapter 8: The Periodic Table
I. Development of the Periodic Table
1. 1864, English chemist John Newlands
1) Newlands noticed that when known elements were arranged in order of atomic
mass, every eighth element had similar properties
2) Law of Octaves
1. Properties of elements repeat as a function of 8 elements
3) Law turned out to be inadequate for elements past calcium
2. 1869, Russian chemist Dmitri Mendeleev and German chemist Lothar Meyer
1) Independently proposed a much more extensive tabulation of the elements based
on the regular, periodic recurrence of properties
3. Mendeleev’s classification was a great improvement over Newland’s for 2 reasons
1) It grouped elements together more accurately, according to their properties
2) It made the possible prediction of the properties of several elements that had yet
to be discovered
4. Modern Periodic Table
1) Shows the atomic number along with the element symbol
1. Atomic number = number of electrons in the atoms of an element
2) Usefulness of the Periodic Table
1. Uses general properties and trends within a group or a period to predict with
considerable accuracy the properties of any element, even though that
element may be unfamiliar to us
II. Periodic Classification of the Elements
1. Categories (according to the type of subshell being filled)
1) Representative Elements (Main Group Elements)
1. Elements in Groups 1 & 2 (s block)
2. Elements in Groups 13-18 (p block)
2) Noble Gases
1. Elements in Group 18
3) Transition Elements (Transition Metals)
1. Elements in Groups 3-12
2. Valence Electrons
1) Outer electrons of an atom involved in chemical bonding
2) Elements in the same group have the same number of valence electrons
1. Also accounts for similarities in chemical behavior among the elements
within each group
3. Electron Configuration of Cations and Anions
1) Ions Derived from Representative Elements
1. One or more electrons are removed from the highest occupied n shell
2. Outermost energy level becomes empty in a representative element cation
3. Isoelectronic Ions/Atoms
1) Ions (or atoms and ions) have the same number of electrons and the
same ground-state electron configuration
2) Cations Derived from Transition Metals
1. Electrons are gained to fill the outermost energy level
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