7.1 and 7.2 Narrated Notes

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Chapter Seven – Part 1 : 

Chapter Seven – Part 1 7.1 – Development of the Periodic Table 7.2 – Effective Nuclear Charge

The Periodic Table : 

The Periodic Table The periodic table is the most significant tool chemists have for organizing and remembering chemical facts Intro

Electron Configurations and the Periodic Table : 

Electron Configurations and the Periodic Table The periodic nature of the table arises from the repeating patterns in the electron configuration of the elements Elements in the same column of the table contain the same number of electrons in their valence orbitals, the occupied orbitals that hold the electrons involved in bonding Intro

Electron Configurations and the Periodic Table : 

Electron Configurations and the Periodic Table Give an example of two elements in the same column having the same valence electron configuration. Give the noble gas configuration for both elements. Intro

The Development of the Periodic Table : 

The Development of the Periodic Table Here is what you need to know How Mendeleev and Meyer arranged their periodic tables What was the significance of blanks left in Mendeleev’s version? 7.1

The Development of the Periodic Table : 

The Development of the Periodic Table Here is what you need to know How Moseley arranged his version of the periodic table What do x-ray frequencies have to do with atomic number? Atomic number is the number of ________ in the nucleus of an atom and the number of electrons in the atom What problems (give specific elements) did Moseley’s version solve? 7.1

Effective Nuclear Charge : 

Effective Nuclear Charge Many of the properties of atoms depend not only on their electron configuration but also on how strongly their outer electrons are attached to the nucleus 7.2

Coulomb’s Law : 

Coulomb’s Law The strength of the interaction between two electrical charges depends on: the signs and magnitudes of the charges the distance between the charges 7.2

Force of Attraction : 

Force of Attraction The force of the attraction between an electron and the nucleus depends on: the magnitude of the net nuclear charge acting on the electrons the average distance between the nucleus and the electron 7.2

Force of Attraction : 

Force of Attraction In a many-electron atom, each electron is simultaneously attracted to the nucleus and repelled by the other electrons 7.2

Effective Nuclear Charge : 

Effective Nuclear Charge The net positive charge experienced by an electron in a many-electron atom; this charge is not the full nuclear charge because there is some shielding of the nucleus by the other electrons in the atom 7.2

Shielding : 

Shielding The electron density that is due to the inner electrons is particularly effective at partially canceling the attraction of the valence electron to the nucleus The inner electrons partially shield or screen the outer electrons from the attraction of the nucleus 7.2

Effective Nuclear Charge : 

Effective Nuclear Charge Zeff = Z – S Zeff is the effective nuclear charge Z is the number of protons in the nucleus S is a positive number called the screening constant and it represents the portion of the nuclear charge that is screened from the valence electrons by the other electrons in the atom 7.2

Effective Nuclear Charge : 

Effective Nuclear Charge Periodic Trends Across a period The nuclear charge increases but the number of core electrons remains the same This results in a steady increase in Zeff Down a group The nuclear charge increases but so does the number of core electrons that shield the valence electrons Zeff increases very subtly as you move down the group 7.2