Chemical Bonding

Joining atoms together to make compounds

Chemical Bonding: combining atoms of elements together to form new substances Bond: force that holds

atoms together to form molecules

Molecules

Two or more atoms that form a new substanceSmallest part of a compound

Review of atomic structure Atoms: electrons, protons, neutrons

Electrons are negatively charged Protons are positively charged Neutrons have no charge

Electrons are in energy levels First level = 2 electrons Second level = 8 maximum electrons Third level = 18 maximum electrons

Valence electrons: the outermost electrons Determine how and with what the atom will bond

Electrons and energy levels video

FACT:

Atoms become stable (won’t react

chemically) when they have a full outer

energy level.

Bohr model review

Start with a circle (nucleus) Put in proper number of protons (atomic

number) Calculate number of neutrons

Atomic mass – mass of protons = neutrons Place electrons:

Start in inner ring, fill first then move to next Start at “12:00”, then “3”, then “6”, then “9” Once shell is half full, electrons pair up

Electron Dot Diagrams Electron dot diagrams used to show how

many valence electrons are in an elementRules:

1. Start with the symbol for the element– Represents nucleus and “inner” energy levels

2. Count how many valence electrons are in the outer shell

3. Place one dot at a time working around the symbol, usually start at “3:00” position

o- -

Electron dot diagramsExamples

Octet Rule: Fill the outer shell to give a total of 8 shared electrons Makes a stable molecule, will not react

further

Types of Bonds Ionic Bonds: transfer of electrons

from one atom to another Ions: Positively or negatively charged atoms

Since negatives and positives attract, the atoms bond to each other

Usually happens between a metal and a nonmetal

Ionic Bonding video

Which elements do you think will bond together?

11P12N e

e ee

e e e e

e e

e

17P18Ne

e

e e e e

e e

e e

e e

ee

ee

e

11P12N e

e ee

e e e e

e e

17P18Ne

e

e e e e

e e

e e

e e

ee

ee

ee

Salt video

Covalent bonding: Sharing electrons equally between two or more atoms

Example: Hydrogen has one valence electron so it needs one more to fill up its energy level Covalent bonds often happen between like

elements Usually happens in non-metals

Cl2, H2, O2

Covalent Bonds video

6P6N

e e e

e

e e 1P

e

6P6N

e e e

e

e e

1P

e

1P e 1P

e

1Pe

6P6N

e e e

e

e e

1P

e

1P e 1P

e

1Pe

6P6N

e e

1P1P

1P

1P

e e

e e

ee

ee

Structural Formula:

shows the actual arrangement of the molecule replace dots between atoms with lines

to indicate the bonds