Valence
Electrons
January 4, 2016
8th grade Chapter 4.1
Meme Moment
Electrons vs Protons
• Both subatomic particles
• Atoms start off with equal numbers of protons and
neutrons
• Protons define what the element is, so they can’t
change
• Electrons define how the element reacts (AKA, its
chemistry)
Electrons, redux
• Not all electrons are equal: we really only care
about the outermost ones
• Outer electrons are called valence electrons
• Valence electrons are easiest to add, remove, or
share because they are far away from the nucleus
• Valence electrons are used in chemical bonds
• Atoms are stable when have a full set of valence
electrons
Periodic Table
Another Periodic Table
We only care about s and p block.
How to Count Valence
Electrons
• Find the element.
• Focus on that row (period).
• Count s+p spots to get to that element.
Periodic Table, cont.
Periodic Table: arrangement of elements showing
shared & repeated properties
Period: a row in the periodic table
Group: a column in the periodic table. Elements in the
same group share chemical properties. Also called a
“family”
Electron Dot Diagrams
• Also called Lewis diagrams
• Draw a dot for each electron
• Dots go on each side, then pair up last
Electrons & Stability
• When an atom has a full set (8) of valence
electrons, it is stable
o H, He, Li, Be are OK with just 2
• If an atom doesn’t have a full set of valence
electrons, it will try to steal, give, or share them with
other atoms
• This makes chemical bonds
o Stealing/giving = ionic bond
o Sharing = covalent bond
• When it’s very close to a full set (alkali metal or
halogen) it will work extra hard and be very
reactive