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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