CH%20301%20Chapter%201%20notes%20part%202 - CH301 Chapter 1...

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CH301 Chapter 1 Notes: Part 2: Trends on the Periodic Table. Electron configurations for the elements underline important properties of the periodic table. This enables us to predict types of bonding and structures of molecules. Similar groups of the elements are classified and named based on their electron configurations . Example: The NOBLE GASES : All are very unreactive. This unreactivity is due to their similar electronic structures. Note every one after He ends with n p 6 . This is a very stable configuration He 1s 2 Ne [He] 2s 2 2p 6 Ar [Ne] 3s 2 3p 6 Kr [Ar] 4s 2 4p 6 Xe [Kr] 5s 2 5p 6 Rn [Xe] 6s 2 6p 6 Representative Elements: (s and p elements) •elements in A groups on periodic chart •their “last” electron is in an outermost* s or p orbital. •have fairly regular variations in their properties. s block elements tend to react with water. Often vigorously! The p -block crosses from metal to nonmetal d -Transition Elements: •in ‘B’ groups on the table •also called transition metals. •electrons being added to lower (inner)* d orbitals (n s (n-1) d configurations) •exhibit smaller row-to-row variations than representative elements* •make IONS by first losing the outer s electrons, then some (amount varies) of the inner d electrons. •Form more than one kind of ion . f - transition metals : •also called inner transition metals. •electrons are being added to lower (inner) f orbitals*. (have n s (n-2) f configurations)•very slight variations of properties from one element to another*. *Outermost electrons have the greatest influence on the chemical properties of elements. METALS AND NONMETALS Review Table 1.4: Properties of Metals and Nonmetals. Learn all the physical properties, and the fact that metals tend to form cations, and nonmentals tend to form anions. All known elements are either METAL, NON-METAL, or METALLOID. Periodic Tables often show a dividing line (see above). “Metallic character” of elements increases as you go DOWN and to the LEFT on the periodic table. Metalloids (e.g., silicon) have the properties of both metals and nonmetals.
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Periodic Properties of the Elements: Atomic Radii (Fig 1.41/1.42) Atomic radii increase within a column going from the top to the bottom of the periodic table. Atomic radii decrease within a row going from left to right on the periodic table. Why are the larger elements’ atoms smaller? EFFECTIVE NUCLEAR CHARGE Consider an atom of Lithium. There are three protons in the nucleus, and three electrons. The configuration is 1s 2 2s 1 which can be written [He] 2s 2 . A positive nucleus attracts negatively charged electrons. Coulombs Law: the force is proportional to the charge and inversely proportional to the square of the distance. Force is greater for greater charge and smaller distance. Consider the 2s electron of Li. Its often further from the nucleus than the two 1s electrons.
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CH%20301%20Chapter%201%20notes%20part%202 - CH301 Chapter 1...

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