Lesson Objectives (6E) Express the arrangement of electrons in atoms using – Electron configurations – Lewis valence electron dot structures Electron Arrangement

Heisenberg uncertainty principle – it’s impossible to know the exact velocity and position of a particle at the same time Atomic orbitals – areas where electrons are likely to be found – Four types of orbitals s, p, d, and f – Quantum numbers – sets of numbers that describe the properties of atomic orbitals and the electrons in them Atomic Orbitals s-orbital shape p-orbital shape d-orbital shapes

Principle quantum number – (n) represents an atomic orbital’s size and principle energy level Electrons that are further away from the nucleus have more energy Electrons in larger orbitals are more likely to be further from the nucleus Principle Energy Levels Larger orbitals = more E nucleus n = 1 n = 2

Principle energy levels can be divided into sublevels – Sublevels are labeled using their principle energy level and orbital type Higher principle energy levels are composed of more sublevels Ex) Principle energy level 1 contains one sublevel Ex) Principle energy level 2 contains two sublevels Quantum Numbers 1s1s n Orbital type { Sublevel 2s 2p2s 2p

Each s sublevel contains one s-orbital Each p sublevel contains three p-orbitals Each d sublevel contains five d-orbitals Each f sublevel contains seven f-orbitals Sublevel Capacities s sublevel p sublevel d sublevel f sublevel

Each orbital can hold up to two electrons – Each s sublevel can hold up to two electrons – Each p sublevel can hold up to six electrons – Each d sublevel can hold up to ten electrons – Each f sublevel can hold up to fourteen electrons Orbital Capacities s sublevel p sublevel d sublevel f sublevel

Electron configuration – describes an atom’s electron arrangement Systems with lower energy are more stable Ground-state electron configuration – arrangement of electrons that gives an atom the least possible energy – Three rules govern how electrons are arranged in ground-state electron configurations: Aufbau principle Pauli exclusion principle Hund’s rule Ground-State Electron Configurations

Electrons achieve their ground-state when they occupy the closest available orbital to the nucleus Aufbau Principle – electrons fill available orbitals with the least energy first Aufbau diagrams show the order of orbitals from least to greatest energy Aufbau Principle

Filling Electron Orbitals 1s 2s2p 3s3p3d 4s4p4d4f 5s5p5d5f 6s6p6d6f 7s7p

Periodic Table Blocks

Orbital Filling Order

Pauli Exclusion Principle Pauli exclusion principle – each orbital can hold a maximum of two electrons – When in the same orbital electrons must have opposite spin – Direction of the electron’s spin is represented the direction of the arrow

Hund’s Rule Negative charges of electrons repel each other Hund’s rule – when filling equal energy orbitals, electrons fill each orbital singly before filling orbitals with another electron in them Energy 1s1s 2p2p 2s2s

Boxes or lines = orbitals Arrows = electrons 1.Determine the highest energy sublevel 2.Draw sublevels in the order they are filled – Determine using periodic blocks 3.Fill orbitals – Number of electrons equals atomic number Ex) Draw the orbital diagram for oxygen Drawing Orbital Diagrams 1s1s 2p2p 2s2s

1.Determine the highest energy sublevel of the atom 2.Write the sublevels in the order they are filled – Determine using periodic blocks 3.Write the number of electrons in each sublevel as a superscript Ex) Write the electron configuration of iron Electron Configuration Notation 1s1s2s2s2p2p3s3s3p3p4s4s 3d3d

Noble gas notation – short hand version of electron configuration notation – Noble gas of the previous period is written in brackets to represent the electron configuration up to that point – Remainder of the electron configuration is written after the noble gas Noble Gas Configuration Notation 4s4s 3d3d 62 Ex) Write the noble gas configuration of iron 222 1s1s2s2s2p2p3s3s3p3p 6 6 Ar

Write the noble gas notation for Iron (Fe)

Valence Electrons Valence electrons – electrons found in the highest occupied energy level Outermost electrons of the electron cloud Establish the chemical characteristics of elements Only electrons represented in Lewis electron dot structures Symbolized by dots

Number of valence electrons is the same as the group number of representative elements Electron Dot Periodic Table

Number of valence electrons is the same as the group number of representative elements Ex) Group 5A elements have 5 valence electrons – N is in group 5A N Writing Lewis Electron Dot Structures

1.Identify the number of valence electrons using the periodic table 2.Place the corresponding number of electron dots around the symbol – First assign one dot per side – If there are still more dots to assign, assign a second dot Ex) Dot Structure for Phosphorus Writing Electron Dot Structures P

Ions form when electrons are lost or gained Ionic charges are based on the number of electrons lost or gained Losing or gaining electrons changes the ratio of positive particles (p + ) to negative particles (e - ) and causes an overall charge to form 10 e - 11 p charge 10 e - 9 p charge Na lost 1 e - to become Na + F gained 1 e - to become F - Ex) Valence Electrons and Ion Formation

Generally, charge can be be determined by an ion’s group number Metals lose valence electrons to form cations Nonmetals gain valence electrons to form anions

Excess or deficit of electrons will be represented by – Number of electrons around the symbol – Charge outside the dot structure Ex) Neutral calcium becomes a calcium ion Ca Ex) Neutral sulfur becomes a sulfide ion S 2- Electron Dot Structures for Ions