Electron Configurations Ch 5.3 CVHS Chemistry

Energy Levels & Sublevels & Spectra Notice Hg & Ne have more spectral lines than H Lines represent energy released when electrons change energy levels Big gaps between lines Represent electrons moving from one energy level to another Small gaps between lines Represent electrons moving from one energy level to a similar level Sublevels Since electrons move around w/in similar energy levels, there must be sublevels within each energy level.

Energy Levels & Sublevels Electrons w/in the same energy level but in different sublevels have similar amounts of energy Sublevels s, p, d, f s has the lowest energy & f has the highest energy Each energy level has the # of sublevels equal to the number of the energy level Energy level 1 has 1s Energy level 2 has 2s & 2p Energy level 3 has 3s & 3p & 3d Look at the shape of each orbital w/in a sublevel. Doesn’t it make sense that it takes more energy for an electron to move in an f pattern than an s pattern?

Electron Configurations A specific # of electrons can fit into each sublevel s Holds 2 electrons p Holds 6 electrons d Holds 10 electrons f Holds 14 electrons

Heisenberg Uncertainty Principle Impossible to measure both the position and energy of an electron accurately at the same time Electron Cloud Model based on the probability of finding an electron in a certain region of space at any given instant In any atom, electrons are distributed into sublevels and orbitals in the way that creates the most stable arrangement; that is, the one with lowest energy

Electron Configurations Electrons fill energy levels and sublevels in an orderly fashion w/ the lowest energy orbitals being filled first This creates the most stable electron configuration The shape of the modern periodic table is a direct result of the arrangement of electrons in the atom.

Electron Configurations The periodic table is divided into blocks that show the sublevels and orbitals occupied by the electrons of the atoms. n represents the energy level and the sublevels are shown as well. Notice how d and f sublevels have lower energy levels than other atoms in their rows, this is because the pattern that the electrons have to move in is more complex than the s and p sublevels. So an atom will put electrons in a higher energy level s or p sublevel before it puts any electrons in the d sublevel

Blank Periodic table Take a moment to fill to fill out a blank periodic table

How to write an electron configuration 1. Find the symbol for the element 2. Write the symbol in brackets for the nearest smaller noble gas 3 Write the outer electron configuration for the remaining electrons.

Practice Electron Configurations Li Be B C N O F Ne

Periodicity Write Noble gas configurations for: Be Mg Ca Sr Ba Ra Elements in the same group or family have similar chemical properties Elements in the same period have similar electron configurations (1 electron is added as you move across the table) This is important because it shows that the periodic trends in properties, observed in the periodic table, are really the result of repeating patterns of electron configuration

Noble Gases Each period ends with a noble gas, so all the noble gases have filled energy levels and, therefore, stable electron configurations

Transition Elements Notice in the periodic table that calcium is followed by a group of ten elements beginning with scandium and ending with zinc These elements begin to fill the 3d sublevel d is very complex so electrons fill 4s and then 3d Metals so they lose electrons and become cations

Inner Transition Elements Two rows at bottom of periodic table lanthanides (atomic numbers 58 to 71) actinides (atomic numbers 90 to 103) These two series are called inner transition elements because their last electron occupies inner-level 4f orbitals in the sixth period and the 5f orbitals in the seventh period

An easy way to remember how atoms fill orbitals & sublevels