Notes on Chemical Bonding

Warm-UpWhat’s an atom? Draw the atomic structure.What is bonding?What is 3 great things about your track-out?

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What’s an atom?• Smallest unit of matter• Made of protons (+), electrons (-),

and neutrons• Has a nucleus and energy shells • Outermost energy shell is called a

valence shell

Quick Review:

• Determine how an atom behaves when it encounters other atoms• reactivity• Determined by group number in

periodic table• Desired number of valence

electrons is 8 (octet rule)

Valence Shells:

Just like the 26 letters of alphabet combine to form words, the 100+ elements combine to form compounds (2 or more different elements)

http://www.brainpop.com/science/matterandchemistry/chemicalbonds/

Chemical Bonding:

an attempt to fill valence shells to “feel noble”

Two types— Ionic bonds Covalent bonds

Chemical Bonding:

A quick simple way to show valence electrons

1 2 13 14 15 16 17 18

H He: Li Be B C N O : F :Ne : Na Mg Al Si P S :Cl :Ar :

Lewis Dot Diagrams:

A. X would be the electron dot formula for

1) Na 2) K3) Al B. X would be the electron dot formula

1) B 2) N 3) P

Learning Check:

Sodium atom Sodium ion

Na – e Na + (feels like Ne)

11 p+ 11 p+

11 e- 10 e-

0 1+

Review Ions:

Fluorine atom Fluorine ion

:F: + e :F: -

(feels like Ne)

9 p+ 9 p+

9 e- 10 e-

0 1-

Review Ions:

Ionic Bonds:

• Ions are the result of atoms gaining or losing electrons

• An ionic bond forms when one atom transfers an electron to another atom

• Occurs when a metal reacts with a non-metal

• The number of electrons lost must be equal to the number of electrons gained

Ionic Bonds cont…• Great conductors of electricity

when dissolved in water• Have very high melting points• Metals will lose electrons, non-

metals will gain electrons• Held together by strong attraction

of (+) to (-)

A. Number of valence electrons in aluminum1) 1 e- 2) 2 e- 3) 3 e-

B. Change in electrons for octet (8 valence)1) lose 3 e- 2) gain 3 e- 3) gain 5 e-

C. Ionic charge of aluminum 1) 3- 2) 5- 3) 3+

Learning Check:

Covalent Bonds:

• A bond formed when electrons are shared between two atoms• Occurs between non-metallic

atoms • Not good conductors of

electricity

Covalent Bonds cont…• Low melting points• Mostly liquids and gases at room

temp (solids are like plastics)• Individual groups of like atoms

formed by covalent bonds are called molecules

A. Covalent bonds are formed when atoms __________ electrons.

1) give up 2) take on 3) share

B. Oxygen would most likely form a covalent bond with

1) Na 2) N 3) Ca

Learning Check:

ionic covalent

valence electrons Sharing electronsTransfers electrons

ions molecules

high mp low mp

conductive Non-conductive

Comparison of Bonds

solids/crystals liquids/gases metals/non-metals non-metals only