How many How many protonsprotons, , electrons,electrons, and and neutronsneutrons

are in an atom?are in an atom?

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Step 1Step 1

Use your periodic Use your periodic table to find an table to find an elementelement

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Step 2Step 2 The number of Protons (+ charge)The number of Protons (+ charge)

The The atomic number = # protonsatomic number = # protons

Kr has 36 protonsKr has 36 protons

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

electronselectrons #protons=#electrons#protons=#electrons Kr has 36 electronsKr has 36 electrons

Step 4Step 4 The number of The number of Neutrons (no charge)Neutrons (no charge) Mass #Mass # (atomic weight rounded to nearest (atomic weight rounded to nearest

whole #)whole #)

Neutrons Neutrons == Mass # Mass # -- ProtonsProtons NeutronsNeutrons == 84 84 – – 3636 Neutrons Neutrons == 48 48

SummarySummary

Number of Number of ProtonsProtons = Atomic # = Atomic # Number of Number of ElectronsElectrons = Protons = Protons Number of Number of NeutronsNeutrons = = Mass #Mass # - -

ProtonsProtons

ProblemsProblems

1.1. Find the protons (p+), electrons Find the protons (p+), electrons (e-), neutrons (n) of Oxygen(e-), neutrons (n) of Oxygen

2.2. Find the p+, e-, n of Xenon (Xe)Find the p+, e-, n of Xenon (Xe)

3.3. Find the p+, e-, n of Zirconium (Zr)Find the p+, e-, n of Zirconium (Zr)

Oxygen (O)Oxygen (O)p+, e-, np+, e-, n

Number of Number of ProtonsProtons = Atomic # = Atomic # Number of Number of ElectronsElectrons = Protons = Protons Number of Number of NeutronsNeutrons = = Mass #Mass # - - ProtonsProtons

Protons = 8Protons = 8 Electrons = 8Electrons = 8 Neutrons = 16-8 = 8Neutrons = 16-8 = 8

Xenon (Xe)Xenon (Xe)p+, e-, n p+, e-, n

Number of Number of ProtonsProtons = Atomic # = Atomic # Number of Number of ElectronsElectrons = Protons = Protons Number of Number of NeutronsNeutrons = = Mass #Mass # - - ProtonsProtons

Protons = 54Protons = 54 Electrons = 54Electrons = 54 Neutrons = 131-54 = 77Neutrons = 131-54 = 77

Zirconium (Zr)Zirconium (Zr)p+, e-, np+, e-, n

Number of Number of ProtonsProtons = Atomic # = Atomic # Number of Number of ElectronsElectrons = Protons = Protons Number of Number of NeutronsNeutrons = = Mass #Mass # - - ProtonsProtons

Protons = 40Protons = 40 Electrons = 40Electrons = 40 Neutrons = 91-40 = 51Neutrons = 91-40 = 51