Download Understanding Atomic Structure of an Element

Understanding Atomic Structure
of an Element
What makes up the Elements of an Atom
• An element is a material that cannot be broken down into
any simpler substance
• Thanks to Dalton, we know that an element is made up of
Atoms that are all identical in mass and no two elements
have the same mass
• Then Thompson and Borh discovered subatomic particles
• Neutrons (n)
• Protons (p)
• Electrons (e)
How an Element is made up
• The atom is made up of three subatomic particles existing in two
main areas
• Nucleus
– Protons: a positively charged particle located inside the nucleus
– Neutrons: contain no electrical charge and is located in the nucleus
• Electron Shells/Orbitals
– Electrons: Negatively charged particles that fill outer orbitals around the
nucleus
Make up of the Atom
• The Nucleus (protons,
neutrons)
– Is only about 1/10,000 of the
size of the atom
• This is equivalent to a pea
contained in a football field
– The Nucleus makes up the
majority of the mass of an
atom
• Electron Shells/Orbitals
– An electron has only 1/1837th
the mass of an proton or
neutron
– Electrons move around on
specific patterns outside of
the nucleus (the majority of
the empty space in an atom)
How to represent an element
• Element: Lithium
– Atomic #3
– This means
• It has 3 Neutrons (n)
• It has 3 Protons (p)
• It has 3 Electrons (e)
• The # of Protons is
what determines
what element
you’re talking about
Mass Number
• Sometimes we will describe an Element by its
mass #
Mass # = Protons + Neutrons
As long as we know two parts of the equations we can solve for the rest (keeping in mind that the
# of Protons is always representative of which element you are dealing with)
Electron Shell Capacities
• Each electron
shell/orbital can
only hold so many
electrons (aka,
Energy Levels)
– First Shell holds 2
electrons
– Second shell
holds 8 electrons
– Third shell holds 8
electrons
– Fourth shell holds
18 electrons
Practice
• Lets do the element Sulfur
– Atomic #16
Valence Electrons
-Valence electrons are those that are contained in the
outer most shell/energy level
-They play a very important role in understanding how a
element will react with other elements in a reaction
-A Valence electron shell is only happy when it contains a
full amount of electrons
Calcium: Atomic #20
2 valence electrons (would
need sixteen more to have a full shell)