Download Section 2.3

Section 2.3
The Modern View of
Atomic Structure
Three Subatomic Particles
• Proton
• Neutron
• Electron
Proton
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•
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Positively charged particle
Located in the nucleus of the atom
Charge of +1.602 x 10-19 C
Expressed in multiples of the charge= +1
Electron
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•
•
•
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Negatively charged particle
Orbit the nucleus of the atom
Account for most of the volume of the atom
Charge of -1.602 x 10-19 C
Expressed in multiples of the charge = -1
Neutron
• Uncharged and electrically neutral particle
• Located in the nucleus of the atom
The Atom
Every atom has an equal number of
protons and electrons, and so atoms
have no net electrical charge.
Mass of the Atom
• Expressed in the atomic mass unit (amu)
1 amu = 1.66054 x 10-24 g
1 g = 6.02214 x 1023 amu
Particle
Charge
Mass (amu)
Proton
Positive (+1)
1.0073
Neutron
None (neutral)
1.0087
Electron
Negative (-1)
5.486 x 10-4
Atomic Number
• References the number of protons in the
nucleus of an atom of a particular element
• Every element has a unique atomic number
Question
• If Pb has an atomic number of 82, how many
protons are in the nucleus of every atom of Pb?
• How many electrons must be orbiting the
nucleus of every Pb atom?
Mass Number
• Total number of protons plus neutrons in the
nucleus of an atom of an element.
• Uses the number of neutrons in the most
abundant form of the element
• How many protons?
• How many electrons?
• How many neutrons?
Isotopes
• Atoms with identical atomic numbers but
different mass numbers