Three rules are used to determine electron arrangement in an atom. Section 3: Electron Configuration...

Three rules are used to determine electron arrangement in an atom.

Section 3: Electron Configuration

KWhat I Know

WWhat I Want to Find Out

LWhat I Learned

• 6(E) Express the arrangement of electrons in atoms through electron configurations and Lewis valence electron dot structures.

Electron ConfigurationCopyright © McGraw-Hill Education

Essential Questions

• How are the Pauli exclusion principle, the aufbau principle, and Hund’s rule used to write electron configurations?

• How do electron-dot structures represent an atom’s valence electrons?


Review• electron


Vocabulary

New• electron configuration• aufbau principle• Pauli exclusion principle• Hund’s rule• valence electron• electron-dot structure

Ground-State Electron Configuration

The arrangement of electrons in the atom is called the electron configuration. The aufbau principle states that each electron occupies the lowest energy orbital available.



The Pauli exclusion principle states that a maximum of two electrons can occupy a single orbital, but only if the electrons have opposite spins. Hund’s rule states that single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same energy level orbitals.


Interactive Table – Electron Configurations and Orbital Diagrams

Concepts in Motion

FPOAdd link to concepts in motion interactive table from page 158 here.


Interactive Table – Electron Configurations

Concepts in Motion




The aufbau diagram can be used to write correct ground-state electron configurations for all elements up to and including Vanadium, atomic number 23.

The electron configurations for certain transition metals, like chromium and copper, do not follow the aufbau diagram due to increased stability of half-filled and filled sets of s and d orbitals.


Valence Electrons

Valence electrons are defined as electrons in the atom’s outermost orbitals—those associated with the atom’s highest principal energy level. Electron-dot structure consists of the element’s symbol representing the nucleus, surrounded by dots representing the element’s valence electrons.


Interactive Table – Electron Configurations and Dot Structures

Concepts in Motion




Electron-Dot Structures

EVALUATE THE ANSWERThe correct symbol for tin (Sn) has been used, and the rules for drawing electron-dot structures have been correctly applied.

Use with Example Problem 3.

Problem Some toothpastes contain stannous fluoride, a compound of tin and fluorine. What is tin’s electron-dot structure?

ResponseANALYZE THE PROBLEMConsult the periodic table to determine the total number of electrons in a tin atom. Write out tin’s electron configuration, and determine its number of valence electrons. Then use the rules for electron-dot structures to draw the electron-dot structure for tin.

SOLVE FOR THE UNKNOWN

Tin has an atomic number of 50. Thus, a tin atom has 50 electrons.

• Write out tin’s electron configuration using noble-gas notation. The closest noble gas is Kr.

[Kr]5s24d105p2

The two 5s and the two 5p electrons (the electrons in the orbitals related to the

atom’s highest principal energy level) represent tin’s four valence electrons. Draw the four valence electrons around tin’s chemical symbol (Sn) to show tin’s electron-dot structure.


Review

Essential Questions• How are the Pauli exclusion principle, the aufbau principle,

and Hund’s rule used to write electron configurations?• How do electron-dot structures represent an atom’s valence

electrons?

Vocabulary• electron

configuration• aufbau principle

• valence electron• electron-dot

structure

• Pauli exclusion principle

• Hund’s rule

Three rules are used to determine electron arrangement in an atom. Section 3: Electron Configuration...

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