Chapter 5: The Structure of Matter Section 1: Ionic Bonds

Bonding of atoms –When two or more atoms join, a bond forms. Bonded atoms are the source of all substances. The kinds of elements in the bond determines the properties of the substance formed. Compounds are made from bonded atoms. The Structure of Matter

When a metal element bonds with a nonmetal element, an ionic bond is formed. –Definition: ionic bond – a bond between oppositely charged ions. –Example: –Sodium has only 1 valence electron. Sodium wants to LOSE this electron! –Chlorine has 7 valence electrons. Chlorine wants to GAIN an electron! SO…. Ionic Bonds

You need this example in your notes. The Structure of Matter Na Has one extra…. Cl Needs one more…

The Structure of Matter Na The two atoms will BOND.. Cl Now Sodium’s 2 nd Energy Level has 8… And Chlorine’s 3rd Energy Level has 8. You need this example in your notes.

–When these two elements bond, Chlorine steals the electron from sodium. Now Sodium has a positive charge and has 8 valence electrons. It is now “happy”. –Chlorine now has a neg. charge. It has 8 valence electrons, and is “happy”. The + and – ions attract each other and form the compound “sodium chloride”. Electron Transfer!

Ionic compounds are usually brittle, and crumble easily. –They also have high melting temperatures.. Ionic Compound Properties

Ionic compounds can conduct electricity in water. –When dissolved in water, the ions come apart. –This allows electricity to flow through them. Ionic Compound Properties

Now that we know how and why ionic bonds form, we can write chemical formulas. Definition: chemical formula – a method of showing the elements that make up a compound. –Example: Na 1 Cl 1 tells us that: Salt is made up of 1 Sodium atom and 1 Chlorine atom. What about MgF 2 ? It is made up of ____ Magnesium atoms and ____ Fluorine atoms. Writing Ionic Compound Formulas

Lets take a closeer look at those compounds. –Na has a charge of 1 +, right? –Cl has a charge of 1 _, right? The charges cancel out! –When an ionic compound forms, it must have the same number of + and _ charges to be neutral. Ionic Compound Formulas

Lets look at how Magnesium and Fluorine bond... Ionic Compound Formulas MG 2+ Magnesium Ion F 1- Fluorine Ion To make a compound with them, you have to make sure the charges cancel. MG 2+ F 1- It takes 1 Magnesium (Mg 1 ) It takes 2 Fluorine (F 2 ) MgF 2

Chapter 5: The Structure of Matter Section 2: Covalent Bonds Sugar is a covalent compound.

When a bond forms between two nonmetal elements, it is called a Covalent Bond. –Water and sugar are two examples of covalent compounds. –Salt is an ionic compound. –Salt does NOT have molecules. –A covalent bond is formed when atoms share one or more PAIRS of electrons. –Covalent bonds are formed in order to fill the outer energy level. Covalent Bonds

Most covalent compounds have relatively low melting temperatures. Covalent compounds do not conduct electricity when melted or dissolved. Molecules are not made up of ions, so they have no charge. Since molecules have no charge, electricity cannot flow through them. Sugar melts easily to become caramel! Properties of covalent compounds.

Some nonmetal elements can form covalent bonds with themselves –For example: –Oxygen can bond with other oxygen atoms by forming covalent bonds. –The atoms will share bonds with each other in order to become happy. Covalent Bonds O. O.... _ _... Each line represents 2 SHARED electrons..... This is the dot diagram for the O 2 Molecule.

Covalent bonds make molecules. –The simplest molecule is H 2. When a molecule is made up of only 2 atoms, it is called “diatomic”. –There are 7 elements that make diatomic molecules with themselves naturally. Covalent Bonds

The Diatomic Elements The 7 Diatomic Elements are: –Hydrogen – H 2 –Nitrogen – N 2 –Oxygen – O 2 –Fluorine – F 2 –Chlorine – Cl 2 –Bromine – Br 2 –Iodine – I 2

When atoms share electrons equally, it is a nonpolar covalent bond. Billy-Bob and Janie-Sue are sharing the shake evenly.

When atoms do not share electrons equally, it is a polar covalent bond. This kid isn’t sharing at all!

In order to name a covalent compound, you add a prefix to the element names. –The prefix you add depends on how many atoms are in the compound. –The element with the most atoms comes 2 nd. –If the 1 st element only has 1 atom, it doesn’t get a prefix. Naming Covalent Compounds

Here are the prefixes for naming covalent compounds: –1 – Mono –2 – Di –3 – Tri –4 – Tetra –5 – Penta –6 – Hexa –7 – Hepta –8 – Octa –9 – Nona –10 - Deca

The Compound CO 2 has: –1 Carbon atom. It does NOT get a prefix. Too bad, Carbon.  –2 Oxygen atoms It gets the prefix “Di” Our compound is called… Carbon Di-Oxide! Example…

The Compound N 2 O 5 has: –2 Nitrogen atoms. It gets the prefix “Di” –5 Oxygen atoms It gets the prefix “Penta” Our compound is called… Di-Nitrogen Pent-Oxide (the a was dropped) Example…

Sometimes, compounds are not just ionic or covalent…they can have both kinds of bonds. –Definition: polyatomic ions – groups of covalently bonded atoms joined by ionic bonds. –Polyatomic ions are written in parentheses. For example: Hydroxide is (OH). Cyanide is (CN) Carbonate is CO 3 The compound Sodium Hydroxide would be written as Na(OH)