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Exploring Exploring Inner SpaceInner Space
TEKS 8.5A describe the structure of atoms including the masses, electrical charges and locations, of protons and neutrons in the nucleus and electrons in the electron cloud
TEKS 8.5B identify that protons determine an element’s identity and valence electrons determine its chemical properties, including reactivity
All matter is made up of atoms.
ProtonsNeutronsElectrons
All atoms are made up of
Each particle has Each particle has specific properties, specific properties, such as location, such as location,
electric charge and electric charge and mass.mass.
All atoms of the All atoms of the same same
element element have same have same number of number of protons. .
*Ex. All Hydrogen atoms have 1 *Ex. All Hydrogen atoms have 1 proton.proton.
The number of protons The number of protons determines the determines the element’s
identity.
atomic number = # of Protons.
Structure of Structure of the Atomthe Atom
The NucleusThe NucleusThe center of the atom is called the nucleus .
proton
neutron
nucleus
3
Li
6.941Lithium
The nucleus contains protons and neutrons.
The nucleus makes up the mass of an atom.
Atomic Mass = # ProtonsAtomic Mass = # Protons + + # # Neutrons Neutrons
Proton = Proton = 11 atomic mass unit (amu) atomic mass unit (amu)
Neutron = Neutron = 11 atomic mass unit (amu) atomic mass unit (amu)
If Lithium has 3 protons and 4 nuetrons, what is the atomic mass of the atom? 7
The Periodic Table shows The Periodic Table shows the atomic mass for each the atomic mass for each element as a element as a decimal. .
Round the atomic mass to mic mass to find the number of find the number of protons or neutrons.protons or neutrons.
If the mass number is known, and If the mass number is known, and you know the number of protons, you know the number of protons, how can you find the number of how can you find the number of neutrons? neutrons? # Neutrons = Mass # - # Neutrons = Mass # - # Protons
The Electron Cloud and The Electron Cloud and Energy LevelsEnergy Levels
Surrounding the nucleus is the electron cloud.
Electrons orbit around the nucleus in different energy
shells (levels).
energy levels
Electrons are so small that they are NOT
included in the atomic mass.
Energy levels can only hold a certain Energy levels can only hold a certain number of electrons in each energy number of electrons in each energy
level.level.
The The first energy level holds up to energy level holds up to 2 electrons. electrons.
The The second energy level holds up to energy level holds up to 8 electrons. electrons.
The The third energy level may hold energy level may hold 8 or more electrons. or more electrons.
first energy level
second energy level
third energy level
8 or more!
How many electrons are in each energy
level of the element Lithium? 1st – 2, 2nd –
1electron
energy levels
3
Li
6.941Lithium
electron cloud
Valence ElectronsValence ElectronsValence electrons are the # of electrons in the outer most energy level.
Valence electrons…..
valence electrons are found here!
Valence electrons Valence electrons determine how determine how reactive it is with other elements. it is with other elements.
Charges on particlesCharges on particles
Protons = Protons = positive charge. charge.Electrons = Electrons = negative charge. charge.Neutrons = have Neutrons = have no charge. charge.
A stable atom has the same number of protons and electrons.
8 Protons++++++++
8 Electron--------
=
NO CHARGE
=
STABLE ATOM
The positive and negative charges cancel out and
there is no charge.
Particle
Charge
Mass
Location
Proton
Neutron
Electron
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