Chem Unit 1

protons

• positively charged (+)

• located in nucleus

• held in nucleus by nuclear force

neutrons

• no charge

• located in nucleus

electrons

• negatively charged (-)

• located in electrons clouds (shells)

quarks

• located in the nucleus

• six “flavors”

• protons & neutrons made of these have a different composition

atomic number (Z)

• included on the periodic table

• # of protons = # of electrons

• is equal to the number of protons and electrons

mass number (A)

• protons + neutrons

• whole number

average atomic mass

• weighted average of that element’s natural isotopes

• are decimals because they are averages!!

isotope

same # of protons, different # of neutrons

atomic symbols

• top number: mass number (protons & neutrons)

• bottom number: atomic number (protons & electrons)