Chemical BondingHow it all comes together!

Ionic Bonding

� Atoms like to become ions with noble gas electron configuration

� Ionic bonding is when ions of opposite charge are attracted to each other

� Electrons are TRANSFERRED between atoms

� There can be no “extra” or “unused” electrons

Introductory Examples

� Lithium has 1 valence electrons

� It wants to get rid of this electron to get to a more stable energy state

� Fluorine has 7 valence electrons

� It wants to fill this empty spot with an electron to get to a more stable energy

state

� Lithium and fluorine make a perfect pair

� If they meet, the electron lithium wants to get rid of will fill the spot fluorine

wants to fill

� Together, they will be LiF-lithium fluoride

Not Always 1:1

� Say we have calcium (wants to get rid of 2 electrons) and fluorine (wants to

get one more electron

� Calcium will give one of its electrons to one fluorine atom and the other

electron to another fluorine atom

� This compound is CaF2 because one calcium atom can “complete” 2 fluorine atoms

� Essentially, we are looking for the lowest common multiple of each charge

Criss-cross Method

� Once we understand why elements form compounds in specific ratios, we can

look at shorter ways of determining the ratios

� Ionic compounds are always between a metal and a non-metal

� The metal comes first in naming and in the formula

� Write the symbol for the metal with its charge in superscript (ignore the sign)

� Write the symbol for the non-metal with its charge in superscript (ignore the sign)

� Switch the numbers and make them subscripts

� Reduce to lowest terms, if applicable

Naming Ionic Compounds

� When naming BASIC ionic compounds:

� Write the metal first (don’t change its name!)

� Write the non-metal second BUT CHANGE its ending to –IDE

� Examples:

� sodium + chlorine yields sodium chlorIDE

� calcium + oxygen yields calcium oxIDE

� ***it is incredibly important that you end these compounds in IDE***

Multi-Valent Ionic Compounds

� Some elements have more than one energy state that is stable

� We call these “multi-valent” elements

� They can take on more than one charge in ion form

� To communicate which ion we are using, we need to include it in the name

� To do so, we use ROMAN NUMERALS

Multi-Valent Ionic Compounds

� Iron is stable with a charge of +3 OR +2

� Each ion forms a very different compound so it is important that we communicate

which one we are dealing with

� If iron (III) combines with oxygen, we call it iron III oxide (Fe2O3)

� If iron (II) combines with oxygen, we call it iron II oxide (FeO)

� Note how the roman number only communicate the CHARGE ON IRON and NOT the

quantity of iron ions involved.

Polyatomic Ions

� Polyatomic Ions are exactly what the name states: ions that have multiple

atoms making them up

� Common examples are: nitrate (NO3-), phosphite (PO3

3-) and ammonium (NH4+)

� These polyatomic ions are always together as a unit, they change in the same

ratio

� If we have 2 (PO33-), it would be (PO3

3-)2

� I recommend ALWAYS WRITING BRACKETS around polyatomic ions before writing any

formulae!!!

Polyatomic Ions and Bonding

� Examples

� Calcium and cyanide: Ca+2 (CN)-1

� Criss-cross OUTSIDE of brackets

� Ca(CN)2

� Aluminum and carbonate: Al3+ (CO3)2-

� Criss-cross OUTSIDE of brackets

� Al2(CO3)3

Combos

� All individual rules apply when coming “special cases”

� If you have a multivalent metal combining with a polyatomic negative ion, you

need to include the roman numeral and maintain the polyatomic ion by using

brackets

Covalent Bonding (after worksheet)

� Covalent bonding is much stronger than ionic bonding

� In covalent bonding, the atoms SHARE their electrons instead of transferring

them

� Depending on the atom, they can share 1, 2, 3, or even 4 of their electrons!

� There are more complex examples that go beyond our curriculum**

� The electrons essentially split their time between atoms, making each atom

believe it has a complete valence shell

� We have looked at this with Bohr diagrams, but Lewis diagram are much more

easily utilized

Covalent Bonding

� Chlorine in its diatomic form

� Cl2

� (draw on board)

� Each chlorine has one spot to fill, they will share one of their electrons with the

other

� Shared electrons are designated with a line

Shared electrons

� Example: carbon tetrachloride

� CCl4

� 1 Carbon, 4 Chlorine

� (draw)

Covalent Bonding (double bonds)

� There are cases when atoms with share more than one electron

� Carbon dioxide

� CO2

� (draw)

� When 2 electrons are shared from between 2 atoms, two lines are used (double

bond)

� When 3 electrons are shared between 2 atoms, 3 lines are used (triple bond)

Naming

� When naming covalent compounds, use the prefixes provided in your data

booklets and add them to the beginning of each element

� ONLY FOR THE FIRST element can the MONO be omitted

� EX:

� H2O>>dihydrogen monoxide

� N2O4>>dinitrogen tetraoxide

� CO>> carbon monoxide

Chemical Formulae

� From a name, you can simply use the prefixes and the element name to write

the compound name

� Examples

� Sulfur hexafluoride >> SF6

� Tetraphosphorus decaoxide >>P4O10

� Dinitrogran monoxide >>N2O