Introduction to Chemical Bonds

Intro to Chemical Bonding

What are Chemical Bonds?

• Force that hold atoms together to form compounds or molecules

• Caused by the attraction from the positive nucleus of one atom to the negative valence electrons of a nearby atom

Multiple Choice

What is meant by "valence electron"?

• electron in the highest energy level

• electron closest to the nucleus

• electron that has a positive charge

• No Idea

Multiple Choice

How many valence electrons do atoms "like" to have?

• 2

• 4

• 6

• 8

Three Types of Bonding

1. Ionic - between metal and nonmetal atoms; electrons are transferred between atoms

2. Covalent - between two nonmetals atoms; electrons are shared

3. Metallic - between metal atoms, usually of the same element; form "sea" of mobile electrons

Multiple Choice

Which of the following is NOT one of the three types of chemical bonds?

• covalent

• ionic

• 007

• metallic

Ionic Bonding

• Electrons are transferred between atoms

• Takes place between a metal AND a nonmetal

• Nonmetal "pulls" the electrons from the metal since it has a much greater electronegativity

• Metal atoms lose electron(s) and becomes positive ion (cation)

• Nonmetal atoms gain electron(s) and become negative ion (anion)

Multiple Choice

Where are non-metals found on the periodic table?

• top left

• top right

• middle d-block

• bottom f-block

Multiple Choice

What type of ion do metals usually form?

• cation

• anion

Multiple Choice

If Cesium and Bromine formed an ionic compound, which would be the cation? Hint:  You may have to look at your periodic table...

• Cesium

• Bromine

Ionic Bonding

• Ionic compounds are NOT considered to be molecules

• ​They are usually many cations and anions held together in a crystal lattice structure

Rock Salt Crystals

Multiple Choice

Ionic compounds like NaCl and CsBr are molecules.

• True

• False

​We can represent the number of valence electrons using what is called an "Electron-Dot Structure" or "Lewis Dot Structure"

​

​Remember, atoms "want" to have 8 valence electrons!

Multiple Choice

How many "dots" would there be on the Lewis Dot Structure of Sodium?

• 1

• 2

• 4

• 5

Multiple Choice

How many electrons would chlorine like to gain to become "happy" (stable)?

• 1

• 2

• 3

• 4

​To form the ionic compound NaCl (sodium chloride)

​

​Na atoms lose their 1 valence electron and become Na+

​

​Cl atoms gain 1 valence electron (that they stole from Na) and become Cl-

​

​The Na+ and Cl- ions are then attracted to each other because they have DIFFERENT charges (opposites attract)

Multiple Choice

What type of ion do you think Calcium forms in an ionic compound?  Hint:  Think about how many valence electrons it has...

• 1+

• 2+

• 1-

• 2-

Covalent Bonding

• Electrons are shared between two or more atoms

• Usually between two or more non-metal atoms - remember non-metals have high electronegativity and they don't want to give up valence electrons

• Form "molecules" of bonded atoms where electron orbitals overlap and share electrons

Multiple Choice

If Nitrogen bonded with Oxygen, would it form a covalent bond or an ionic bond?

• covalent

• ionic

Multiple Choice

How many covalent bonds would Sulfur (S) "want" to make? Hint:  How many valence electrons does it have and how many does it want...

• 1

• 2

• 3

• 4

Sulfur has 6 valence electrons

It would likely form 2 covalent bonds if it bonded with another non-metal

Multiple Choice

How many Hydrogen atoms do you think a Carbon would bond with?

• 0

• 1

• 2

• 4

​Carbon has 4 valence electrons and LOVES to form 4 covalent bonds so that it can have a full octet (8) valence electrons

Metallic Bonding

• Usually forms between the same type of metal atoms

• Metal atoms have same/similar electronegativities so they can't "steal" valence electrons from each other

• Scientists now believe that the valence electrons of metal atoms form a "sea" of mobile electrons (- charges) throughout the metal cations (+ charges)

Multiple Choice

Metals have many practical uses for us. Which is a direct result of this "sea of mobile electrons"?

• Pretty colors when ions form

• Electricity moving thru metal wires

• Gold being really expensive

• No idea

Multiple Choice

Which type of bond do you think is the strongest?

• ionic

• covalent

• metallic

​Let's up the stakes a bit...

​The next few questions are review from past units but will be important in this one

THESE ARE WORTH DOUBLE POINTS!

Multiple Choice

What is meant by electronegativity?

• The attraction of an atom to electrons of other atoms

• The energy required to lose an electron

Multiple Choice

Which of the following has the lowest electronegativity?

• oxygen

• magnesium

• sulfur

• strontium

Multiple Choice

How many valence electrons do most d-block elements have?

• one

• two

• eight

• No Clue

Then End​

​But there is more about Bonds...