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?
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17P18Ne
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17P18Ne
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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
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6P6N
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Structural Formula:
shows the actual arrangement of the molecule replace dots between atoms with lines
to indicate the bonds