Chemical Bonds

Regents Review Book: Chapter 4

Chapter 5 – Page 157

Types of Chemical Bonds

We will study 4 types of chemical bonds: Ionic Bonds

Bonds between metals and non-metals Electrons are transferred

Covalent Bonds Bonds between two non-metals Electrons are shared

Metallic Bonds Bonds between two metals

Intermolecular Bonds Bonds between molecules

Chemical Reactivity

Some chemicals are reactive and some are not Name the most reactive metal on the

periodic table:____________________

Name the most reactive non-metal on the periodic table:____________________

Name the non-reactive gases on the periodic table:___________________________

Chemical Reactivity

Why are the noble gases not reactive?

________________________________________________________________________________________________________________________________________________

Draw the Bohr model of the outer valence shell of Neon:

Chemical Reactivity

If the noble gases are not reactive due to their outer shell configuration, then the alkali metals and halogens must be very reactive because:

______________________________________

______________________________________

______________________________________

Chemical Reactivity

Draw the Bohr model outer shell valence configurations for sodium and fluorine:

Sodium Fluorine

If sodium loses its one valence electron, will it have a full outer energy level? _______

If fluorine gains one valence electron, will it have a full outer valence energy level? ________

Chemical Reactivity

Does having a full outer valence electron configuration make an atom more stable?

Why?

OCTET RULE: a concept of chemical bonding theory that assume that atoms want to have the full electron configuration of the noble gases: 8 outer (valence) electrons

Chemical Reactivity

Why doesn’t sodium try to gain seven more electrons rather than giving one away?

______________________________________________________________________________________________________________________________________________________________________________________

Why can fluorine gain electrons?

Chemical Reactivity

Please note: Hydrogen can gain or lose an electron Helium is stable because its valence shell is

full with only two electrons (it only has 2 protons).

Lithium (three protons) and Beryllium (4 protons) will also be stable with only two electrons in their valence shell.

IONS

Charged particles are called IONS Loss of an electron makes the atom more

positive so it is called a positive ion.In our example, sodium loses an electron. The way to write a positive ion is as follows:

Na+1

Symbol of element Charge on the ion

The EQUATION for this reaction is:

Li → Li+ + e-

Cation – Positively Charged Ion

IONS

Gain of an electron makes the atom more negative, so it is called a negative ion.

Cl-1

The equation for this reaction is:

F + e- → F-

Symbol of element

Charge on the ion

Anion – Negatively Charged Ion

Valence Electrons

Electrons that are found in the outermost shell of an atom; they determine the atom’s chemical properties because:

Valence electrons are the electrons involved in chemical bonding!

Inner electrons are not involved in bonding

Transition Elements

Not all elements must have a noble gas configuration to be stable – these are called the transition elements.

Many transition metals are stable even though they do not have noble gas configurations.

Ex: Copper can give up one or two electrons when bonding; both cations are stable even without a noble gas configuration.

Color of copper whenit gives up one electron

Color of copper when it givesup two electrons

IONS vs. ATOMS

Atoms and Ions have different propertiesExample:Sodium metal and chlorine gas are very reactive and dangerous.

Sodium chloride (NaCl) is an ionic compound that is NOT dangerous BECAUSE IONS HAVE DIFFERENT PROPERTIES THAN THEIR PARENT ATOMS

General Information About Bonds

Chemical bonds have stored (potential) energy

Energy must be absorbed to break a chemical bond

Energy is released during bond formation

Ionic Bonds

When a metal atom transfers electrons to a non-metal atom, an IONIC BOND is formed

The two atoms are attracted by their opposite charges

http://www.teachersdomain.org/asset/lsps07_int_chembonds/

Ionic Bonds

Do the two atoms in the previous slide have fuller outer octets?

Does this make sodium chloride stable or unstable?

Bond Character

An ionic bond occurs when the electronegativity difference between its atoms is 2.0 or greater.

Example: Electronegativity of Sodium: ___________ Electronegativity of Chlorine: ___________ Difference in Electronegativity ___________

Based on the above information, is this an ionic bond?_______________

Ionic Bond Summary

1. Formed by the ___________________of electrons.

2. Form when a ___________________ion and _____________________ion attract each other.

3. Have an electronegativity difference of _________or more.

Ionic Salts

Atoms in an ionic compound tend to arrange themselves in specific orderly patterns (crystalline structures) and form salts

Ionic Salts

Salts are Hard and Brittle (pg 173) Crystals are arranged in

repeating patterns, which form layers

Each cation is positioned next to an anion

The attractive force between these oppositely charged ions make it very strong

It takes a lot of energy to break these bonds

Properties of Ionic Substances (salts)

MEMORIZE THE FOLLOWING!!!

1. All are solid at room temperature.

2. Are hard and brittle; should not break easily. If it does break, it is into smaller crystals.

3. Have high melting and boiling points.

4. Ionic compounds that are melted will conduct electricity.

5. Ionic compounds dissolved in water will conduct electricity.

6. Will dissolve in polar compounds.