Parts of the Atom and The Periodic Table

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Nucleus

• Center of the atom. • Makes majority of the atom’s mass.• Made of Protons and Neutrons.

Nucleus

Protons

• Part of the nucleus• Have positive (+) charge• Protons are the atomic number on the PT• Protons = number of electrons

Neutrons• Part of the nucleus• Have neutral charge• Varying neutrons make isotopes• Find neutrons - Atomic Mass – Atomic

Number (protons) = Neutrons

Mass Number

• Part of the nucleus• Number of protons + neutrons

Isotopes• Atoms with the same number of protons

but different numbers on neutrons• So you can change the number of

neutrons and the element still maintains its identity

• Example: Carbon

Electrons

• Orbit around the nucleus• Have negative (-) charge• Electrons = the number of protons

Electrons – Energy Levels

• Energy levels are in the electron cloud and around the nucleus

• Each level has a set number of electrons that the level can hold up to

• Outer most level is for chemical bonding• Energy levels are

accurate until the 5th energy level

Atoms have neutral charge• # of Protons (+) = # of Electrons (-) = 0 charge

• Example: Hydrogen

• How many electrons does C have?

Electrons orbit in “shells”• 1st shell can fit 2 electrons

• 2nd shell can fit 8 electrons2nd period/row

3rd period/row

1st period/row

• 3rd shells can fit up to 18 electrons

Reading and Using the Periodic Table

Mass

Atomic Number

• Definition: the number of protons in the nucleus

• Protons = Atomic Number = Electrons• Tells us the identity of the element.

Every element is defined by the number of protons in its nucleus

Atomic Mass

• Definition: the ~ mass of one atom of an element

• Tells us how much one atom weighs in atomic mass units.

Mass