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CHAPTER 8 Periodic Properties of the Elements

Chemistry (Custom UMD Edition) #

Nivaldo J. Tro#

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•  Coulomb’s Law describes the attractions and repulsions between charged particles#

•  For like charges, the potential energy (E) is positive and decreases as the particles get farther apart as r increases#

•  For opposite charges, the potential energy is negative and becomes more negative as the particles get closer together#

•  The strength of the interaction increases as the size of the charges increases#

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• Each electron in a multielectron atom experiences both the attraction to the nucleus and repulsion by other electrons in the atom#

• These repulsions cause the electron to have a net reduced attraction to the nucleus – it is shielded from the nucleus#

• The total amount of attraction that an electron feels for the nucleus is called the effective nuclear charge of the electron#

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The periodic table is "blocked-out" in terms of the outermost electrons of the electronic configuration

of the elements. "

(n)S-Block

(n)P-Block (n-1)d-Block

(n-2)f-Block

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1#1#s#

value of n#value of l#

no. of#electrons#

spdf (or spectroscopic) notation#for H, atomic number = 1#

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Arrowsdepictelectronspin

ORBITAL BOX NOTATIONfor He, atomic number = 2

1s

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Ne # #Mn # #Zn # #Eu#

1s22s22p4 1s22s22p6 [Ar]184s23d1

[Kr]365s24d6 [Xe]546s24f145d106p5

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1s

2s

3s3p

2p

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•  Movement of ions across cell membranes is the basis for the transmission of nerve signals

•  Na+ and K+ ions are pumped across membranes in opposite directions through ion channels

•  Na+ out and K+ in •  The ion channels can differentiate Na+ from K+

by their difference in size •  Ion size and other properties of atoms are

periodic properties – properties whose values can be predicted based on the element’s position on the Periodic Table

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decreases

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X(g) + Eionization X+(g) + e-

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•  Metals tend to lose electrons in reactions (low IE).

•  Nonmetals tend to gain electrons (high IE).

•  Metal oxides are basic in aqueous solutions.

•  Nonmetal oxides are acidic in aqueous solutions.

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Isoelectronic: have the same number of electrons

Main group elements tend to become ions that are isoelectronic to their nearest noble gas element.

Na (1s22s2p63s1) Na+(1s22s2p6)

Larger main-group metals and transition metal tend to form pseudo inert-gas configurations:#

#[inner shell]ns2np6(n-1)d10#

Sn (..4s24p65s24d105p2) Sn4+((..4s24p64d10)

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•  Ions, such as the transition metal ions, first lose electrons with the highest n value:

•  Main group-s-block: remove all electrons with the highest n value.

•  Main group-p-block: remove np electrons before ns electrons.

•  Transition metals: remove ns electrons before (n-1)d electrons.

•  Nonmetals: add electrons to the p orbitals of the highest n value.

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Fe3+ ions in Fe2O3 have 5 unpaired electrons and make the sample paramagnetic.#

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