How many protons, electrons, and neutrons are in an atom? http://physicsed.buffalostate.edu/Wiley/CJ6e/img30/PTE.gif

Step 1 Use your periodic table to find an element http://education.jlab.org/qa/pen_number.html

Step 2 The number of Protons (+ charge) The atomic number = # protons Kr has 36 protons http://education.jlab.org/qa/pen_number.html

Step 3 The number of Electrons (- charge) Remember atoms have no overall charge. Atoms must have an equal # of protons and electrons #protons=#electrons Kr has 36 electrons

Step 4 Neutrons = Mass # - Protons The number of Neutrons (no charge) Mass # (atomic weight rounded to nearest whole #) Neutrons = Mass # - Protons Neutrons = 84 – 36 Neutrons = 48

Summary Number of Protons = Atomic # Number of Electrons = Protons Number of Neutrons = Mass # - Protons

Problems Find the protons (p+), electrons (e-), neutrons (n) of Oxygen Find the p+, e-, n of Xenon (Xe) Find the p+, e-, n of Zirconium (Zr)

Oxygen (O) p+, e-, n Number of Protons = Atomic # Number of Electrons = Protons Number of Neutrons = Mass # - Protons Protons = 8 Electrons = 8 Neutrons = 16-8 = 8

Xenon (Xe) p+, e-, n Number of Protons = Atomic # Number of Electrons = Protons Number of Neutrons = Mass # - Protons Protons = 54 Electrons = 54 Neutrons = 131-54 = 77

Zirconium (Zr) p+, e-, n Number of Protons = Atomic # Number of Electrons = Protons Number of Neutrons = Mass # - Protons Protons = 40 Electrons = 40 Neutrons = 91-40 = 51