Protons• Positive Charge• Located in the nucleus• Mass = 1 amu– Helps make up the mass of an atom
• # of protons never changes for an element– Same as atomic number
Neutrons• No Charge• Located in the
nucleus• Mass = 1 amu– Helps make up the
mass of an atom– Can differ in atoms of
the same elementHow to Calculate
NeutronsMass # - Atomic # = Neutrons
Electrons• Negative Charge• Located in the electron cloud– Surrounds the nucleus– Move very fast!
• Mass = 0 amu– Does not really count towards an atom’s mass
• In neutral atoms, electrons = protons
Atomic Number• Special for every element
• Tells # of protons (and electrons)• Located on the periodic table (whole number)
Practice•Name of Element:
•Atomic Number:
•Atomic Mass:
•Mass Number:
•Protons:
•Neutrons:
•Electrons:
Practice•Name of Element:
•Atomic Number:
•Atomic Mass:
•Mass Number:
•Protons:
•Neutrons:
•Electrons:
Practice•Name of Element:
•Atomic Number:
•Atomic Mass:
•Mass Number:
•Protons:
•Neutrons:
•Electrons:
Isotopes• Same element with different numbers of
neutrons; therefore, different masses• EX: Carbon-12 Carbon-14
6 12 C 6 14 C
PracticeHow many electrons in a neutral
atom of Na?
How many protons in Na?
How many electrons in Na +1