Filling the orbitals 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p ...

Atomic Structure, Periodicity and Chemical Reactivity The outermost electron shell is called the valence shell electrons in the valence shell are called valence electrons The group the element is in tells us how many valence electrons it has Lewis structures draw dots around the atom which represent the valence electrons Be, C, Ne, F- , O2-

Atomic Structure, Periodicity and Chemical Reactivity The noble gases are inert (do not chemically react) Have a full shell - most stable There are eight electrons in the outer shell (ns2 np6 = 8) Octet rule - a valence shell is energetically stable when it has 8 electrons Non-metals want an octet (usually)

Ionic Bonds Ionic bond is a strong electrostatic attraction between a positive ion and a negative ion Formed when an electron is donated from one atom’s outer shell and accepted by another atom (the octet rule) Na + Cl  NaCl

Donate or Accept Electrons Ionization energy - the amount of energy it takes to remove a mole of electrons from a mole of gaseous atoms. - Atoms on the right of the periodic table have a high ionization energy (accept) - Atoms on the left have low ionization energy (donate)

Ionic Compounds and Formulas Rule - Net electrical charge must be zero (total positive charge must be equal to total negative charge) Li + F Li gives 1 electron to F Forms LiF (Lithium Fluoride) Mg + F Mg gives 1 electron to each F (2 total) Forms MgF2 (Magnesium Fluoride) Al + F Al gives 1 electron to each F (3 total) Forms AlF3 (Aluminum Fluoride) Al + O Al gives 2 electrons to each O (6 total) Forms Al2O3 (Aluminum Oxide) Al + N Al gives 3 electron to N (3 total) Forms AlN (Aluminum Nitride)

Naming Binary Ionic Compounds Binary means two different type of elements (NaF or MgO) Name of the metal element is included unchanged Name of the nonmetal is is combined with the suffix -ide LiF - Lithium Fluoride MgCl2 - Magnesium Chloride Na2S - Sodium Sulfide

Group Work Write the Lewis Dot reaction, formula and product name for the following K + Br Ca + I Rb + O Ba + N Li + Ar (this one is tricky)

Polyatomic ions An ion that consists of two or more atoms combined into a single charged unit is called a polyatomic ion

Formula of an Ionic Compound Does NaCl only have one Na and one Cl? Ionic compounds, as solids, are packed together with cations surrounded by anions and anions surrounded by cations. The net charge of the solid is neutral. NaCl (or any ionic formula) only gives the simplest form of the ionic compound (no molecule of NaCl) CD - animation When liquid or dissolved, the ions break apart from each other and behave as individual ions

Covalent Bonds Covalent bond is a bond formed when electrons are shared between atoms H + H forms H2