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Every atom wants to be “happy” or stable (have their outer energy level full) An element can accomplish this in one of two ways: 1) Electrons can be transferred from one atom to another so that they both atoms become happy. 2) Electrons can be shared between atoms so that they both atoms become happy.

When electrons are transferred from one atom to another so that both atoms become happy, this is called an IONIC BOND.

When electrons are shared from one atom to another so that both atoms become happy, this is called a COVALENT BOND.

An ionic bond occurs between a metal (sodium) and a nonmetal (chlorine)

An ionic bond occurs when electrons are transferred from one atom to another (usually a nonmetal TAKES electrons from a metal)

Metals have low ionization energies and lose electrons easily. Non-metals have high electron affinities (the ability of an element to attract electrons). Therefore, it takes an electron(s) away from the metal so that they both become happy or stable. An ionic bond IS NOT a physical bond, rather an attraction (closeness) between ions of opposite charge. Example: Na +1 and Cl -1

How Does Ionic Bonding Occur? Let’s consider Potassium (K) What does Potassium want to do in order to become happy or stable? K is a metal & wants to lose its one valence electron What would be the ionic charge for Potassium? +1 ( +19 p – 18 e- ) (Loses electrons)

Now consider Fluorine (F) What does Fluorine want to do in order to become happy or stable? F is a non-metal & wants to GAIN its one valence electron What would be the ionic charge for Fluorine? -1 ( +9 p – 10 e- ) (Gains electrons) How Does Ionic Bonding Occur?

What will happen between the potassium and fluoride ions? Opposite charges attract. Thus, these two ions will form an ionic bond. How Does Ionic Bonding Occur?

Each ion can be represented with a symbol. List the cation (+) first and then the anion (-) last. Write a formula to represent the ionic bond.

Naming Ionic Compounds is quite simple … Name the metal first (as is) Name the non-metal second (change the end of the non-metal to –ide). K +1 F -1 Potassium Fluoride

K +1 F -1 Potassium Fluoride The chemical equation for this ionic compound is K 1 F 1 or simply KF because it takes 1 potassium to make 1 fluorine happy.

Let’s Do Another Example… Magnesium (Mg) What does Mg want to do in order to become happy or stable? Mg is a metal & wants to lose its TWO valence electrons What would be the ionic charge for Magnesium? +2 ( +12 p – 10 e- ) (Loses electrons)

Oxygen (O) What does Oxygen want to do in order to become happy or stable? Oxygen is a non-metal & wants to GAIN its TWO valence electrons What would be the ionic charge for Oxygen? -2 ( +8 p – 10 e- ) (Gains electrons) Forming an Ion

Oxygen takes 2 electrons from Magnesium (because Oxygen has a higher electron affinity). The two ions attract because of their opposite charges. How Does Ionic Bonding Occur?

Each ion can be represented with a symbol. List the cation (+) first and then the anion (-) last. Write a formula to represent the ionic bond.

Naming Ionic Compounds … Name the metal first (as is) Name the non-metal second (change the end of the non-metal to –ide). Magnesium Oxide Mg +2 O -2

Up until this point, all the atoms we used formed an ionic bond that had equal and opposite ionic charges (Example: Mg +2 and S -2 ). What happens if different elements form different ionic charges? Will they still form an ionic bond? Lithium Phosphorus

LithiumPhosphorus We will use Lewis Dot Structures to show how this will work. Lewis dot structures plot ONLY the valence electrons of an element Li P

Lithium has one valence electron … therefore, one “dot” Phosphorus has 5 valence electrons (NEEDING 3 MORE) … therefore, 3 dots Lithium can give its electron to Phosphorus becoming a +1 ion It takes 3 Lithium atoms to FILL the valence of 1 Phosphorus atom, making it stable. Therefore, the chemical formula is Li 3 P We can name this ionic compound: Lithium Phosphide Li +1 P Li P -3 Li +1 Li +1

Beryllium Nitrogen Be N What if we use Beryllium and Nitrogen? Beryllium has 2 valence, therefore its Lewis Structure has 2 dots Nitrogen has 5 valence electrons, its Lewis Structure has 5 dots Clearly, these atoms cannot bond 1:1

Beryllium is a metal and will lose its electrons, becoming a positive ion. Nitrogen is a non-metal and will take the electrons from other atoms, becoming a negative ion Find a common multiple between the two ion charges (2 x 3 = 6). 6 electrons need to be transferred for both elements to be stable. This means we need 3 Beryllium atoms and 2 Nitrogen atoms. Beryllium Nitrogen Be +2 N -3 N

The chemical formula for the above ionic compound is: Be 3 N 2 The name of the ionic compound is: Beryllium Nitride Be +2 Be +2 NN N -3 N Be +2

Instead of using Lewis Dot Structures to show how two elements become stable, there is an easier way … Magnesium Fluoride

1.Find the ionic charge of Sodium & Phosphorus 2.Criss-Cross (or swap) the numbers from one element to the other. 3.Superscript #’s become subscripts (don’t have to write 1’s) Sodium Phosphide

1.Find the ionic charge of Aluminum & Oxygen 2.Criss-Cross (or swap) the numbers from one element to the other. 3.Superscript #’s become subscripts (don’t have to write 1’s) Aluminum Oxide

1.A covalent bond occurs between 2 nonmetals OR between a nonmetal and hydrogen. 2.Electrons are shared to make both atoms stable. 3.Notice that each bond represents TWO shared electrons.

Electron affinity of non-metals and hydrogen are relatively the same. Therefore, they are not strong enough to take away electrons from another element. Thus, they share electrons. A covalent bond IS a physical bond because the elements share electrons

Covalent Bonding Examples… FluorineChlorine Both Fluorine and Chlorine want 1 electron to FILL their valence. This means that each can have ONE covalent bond. Therefore, these two atoms will form a SINGLE covalent bond. FCl F Cl FCl The Dash represents 2 shared electrons

Covalent Bonding Examples… HydrogenOxygen Hydrogen needs 1 electron to FILL its valence. This means it can have ONE covalent bond. Oxygen needs 2 electrons to fill its valence and can have TWO covalent bonds. O Each pair of 2 shared electrons becomes a bond H O HHHO H

Nitrogen Nitrogen bonds with itself in nature to form N 2. Each Nitrogen atom needs 3 electron to FILL its valence. This means it can have THREE covalent bonds. Nitrogen NN N Each dash represents 2 shared electrons that became a bond

Carbon C C Each Carbon atom needs 4 electrons to FILL its valence. This means it can have FOUR covalent bonds. Carbon almost always produces 4 covalent bonds

Carbon C When Carbon bonds with hydrogen, it needs 4 electrons to fill its valence Hydrogen needs 1 electron to fill its valence. Therefore, 4 hydrogen atoms bond to 1 carbon atom C H HH H Hydrogen H

Carbon C How does Carbon Dioxide form (CO 2 )? Oxygen needs 2 electrons to fill its valence. Therefore, 1 carbon atom bonds with 2 oxygen atoms to fill the valence of each atom. Oxygen O COO