Chemical Bonding Chapter 13

Electrons and Chemical Bonding section 1

Combining Atoms Through Chemical Bonding All substances are made of atoms of one or more the approximately 100 elements carbon, hydrogen, and oxygen combine to make sugar, alcohol and citric acid chemical bonding is the joining of atoms to make new substances

properties of these new substances are different from the original substances An interaction that holds 2 atoms together is called a chemical bond Chemical bonds form when electrons are gained, lost, or shared

Discussing Bonding Using Theories and Models atoms and chemical bonds cannot be seen with the unaided eye for 150 years scientists have done experiments to help develop theories of chemical bonding models used to help form theories

Electron Number and Organization To understand how chemical bonds form, you need to know about the electrons Electrons in an atom are organized in energy levels models are useful for counting electrons in energy levels

Outer Level Electrons and Bonding Not all of the electrons in an atom can make chemical bonds Atoms bond using only the electrons in the outer most energy level valence electrons are the electrons in the outer most energy level

Valence Electrons and the Periodic Table You can use the periodic table to determine the number of valence electrons of some elements Elements are grouped by similarities within group there are the same number of valence electrons Group numbers can help determine the number of valence electrons

To Bond or Not To Bond Not all atoms bond in the same way The number of electrons in the outer energy level will determine whether an atom will bond Noble gases usually don't form chemical bonds have 8 valence electrons (except for Helium) outer level is considered full if it has 8 valence electrons

Filling the outermost level an atom with fewer than 8 valence electrons is more likely to form bonds atoms bond by gaining, losing or sharing electrons to have a filled outer most energy level

Is Two Electrons a Full Set? Not all atoms need 8 valence electrons Helium only needs 2 Hydrogen, and lithium can form bonds with only 2 valance electrons

Valence Numbers vs. Oxidation Numbers Valence number= is the number of electrons in the outer energy level Oxidation number = is the number of electrons it will give or take Na O valence- 1 valence - 6 oxidation +1 oxidation -2