Atomic Masses 16.2

Quark – smaller particles that make up protons and neutrons Smaller particles of matter called quarks exist, but scientists still consider atoms the basic building blocks of matter.   Quark – smaller particles that make up protons and neutrons – six quarks are known to exist

Atomic number – the number of protons in an atom Atomic mass – composed mostly of protons and neutrons in the nucleus – called the mass number   Atomic number – the number of protons in an atom Elements are identified by their atomic number

Atomic number = # of protons # of electrons = # of protons If you need to find # of neutrons of an atom: # of neutrons = mass number – atomic number Atomic number = # of protons # of electrons = # of protons # of neutrons = mass number – atomic number

Isotopes – atoms of the same element that have different number of neutrons Ex: B10 or B11 Boron-10 Boron11 Different isotopes have different properties.  

Average atomic mass – weighted average mass of an element’s isotopes Common Mass Numbers Element Symbol Atomic # # Protons # Neutrons Mass # Avg. Atomic Mass Boron B 5 6 11 11.81 amv Carbon C 12 12.01 amv Oxygen O 8 16 16 amv Sodium Na 23 22.99 amv Copper Cu 29 34 63 63.55 amv

Construct a time line that will show the development of the atomic theory. Include: date, name of scientist, statement of their theory, illustration of their model Do Now