Unit 3 – Electron Configuration and Ionic Compounds

Unit 3 – Electron Configuration and Ionic Compounds principal energy level – major energy levels of an atom This is EXACTLY the same as the period on the periodic table. How many energy levels does bromine have? What about iridium?

Energy Sublevels Each energy level has sublevels. Energy level 1 has ___ sublevel Energy level 2 has ___ sublevels and so on… sublevel 1 is the ___ sublevel 2 is the ___ sublevel 3 is the ___ sublevel 4 is the ___

Orbitals Each sublevel has orbitals which are specifically where the electrons are located. s sublevel has ___ orbital p sublevel has ___ orbitals d sublevel has ___ orbitals f sublevel has ___ orbitals sublevels are also known as subshells

Orbitals INCREASING ENERGY orbital The 1st energy level has 1 sublevel: 1s (with 1 orbital). The 2nd energy level has 2 sublevels: 2s (with 1 orbital) and 2p (with 3 orbitals). The 3rd energy level has 3 sublevels: 3s (with 1 orbital), 3p (with 3 orbitals), and 3d (with 5 orbitals). and so on… energy level sublevel

Filling in Electrons aufbau principle – electrons occupy the lowest energy orbital available From the previous page, electrons will occupy the 1s orbital before the 2s orbital, the 2s orbital before the 2p orbital, and so on... Note, however, that the 4s orbital is lower energy than the 3d orbitals. Therefore, electrons will actually fill the 4s orbital first. To help with this, there’s yet another diagram…

Filling in Electrons Pauli exclusion principle – max of two electrons can occupy one orbital and they must have opposite spins means spin in one direction means spin in the opposite direction So to fill one orbital, the electrons must look like this:

Filling in Electrons Hund’s rule – an orbital cannot hold two electrons until each orbital in that sublevel has at least one electron For example, fill in the following p orbitals with 4 electrons:

Ions To become more stable, some atoms gain or lose electrons to achieve a full octet. ion – atom or group of bonded atoms that have a net charge cation – ______________ charge anion – ______________ charge

Ions octet rule – stable atom or ion has _____ electrons in its highest energy level All atoms want to look like nearest noble gas in terms of electron configuration. They gain or lose electrons – i.e. form ions – or share electrons (whichever is easiest) to accomplish this. Helium is an exception – it is stable but only has _____ valence electrons. The valence shell is full though so that’s what really counts.

Charge Pattern in Groups Transition Elements don’t follow this pattern but they always have positive charges.

Forming Compounds compound – chemical combination of elements The subscript tells how many atoms of a particular element are in the compound. No subscript means that there is one atom. H2O NaCl H2SO4 4 oxygen atoms 2 hydrogen atoms 1 oxygen atom 1 sodium atom 1 chlorine atom 2 hydrogen atoms 1 sulfur atom

Forming Compounds All you do is cross the numbers in the charge. Al S Na Cl Sr F Ba O K P Cs I Positive ion is ALWAYS first!

Polyatomic Ions definition – ions comprised of more than one atom They act exactly like normal ions but you have to keep the polyatomic ion atoms together when you use subscripts…

Polyatomic Ions H NO3 Ca CO3 C2O4 Al Na C2H3O2 NH4 S Positive ion is still first!

Naming Ionic Compounds Cation is always first, anion is always second. For compounds WITHOUT polyatomic ions, these have just two elements: Step 1: name of the cation Step 2: name of the anion Step 3: change the end of the anion to “-ide”

Naming Ionic Compounds NaCl AlBr3 Ca3N2 MgO LiI

Naming Ionic Compounds For compounds WITH polyatomic ions: Step 1: name of the cation Step 2: name of the anion Don’t change either word.

Naming Ionic Compounds Na2CO3 Al2(NO3)3 KOH Mg(C2H3O2)2 SrSO4

Naming Ionic Compounds CaO Li2SO4 NaHCO3 Fe2S3 Ba(NO3)2

Unit 3 – Electron Configuration and Ionic Compounds