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The Atom and its Structure . Components of an atom. Atoms are made of Protons Electrons Neutrons . Symbols and Atomic Structure
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Components of an atom • Atoms are made of • Protons • Electrons • Neutrons
Symbols and Atomic Structure • Isotopesare atoms of an element with identical chemical properties, but different masses due to a difference in the number of neutrons. • The atomic mass of an element is the average of all the atomic masses of the isotopes. • an isotopes contribution is determined by its relative abundance.
The mass of an element is the mass of the element compared to an isotope of Carbon 12. • Carbon 12 is assigned an atomic mass of 12.00 g. • 12.00 is one atomic mass unit • The number of protons and neutrons in an atom is its mass number. • Atomic numbers are whole numbers • Mass numbers are whole numbers
Charge (if ion) Atomic Mass(mass number) Symbol Atomic Number
Hydrogen Protons: 1 Neutrons: 0 Electrons: 1 H 1 1
Sodium Protons: 11 Neutrons: 12 Electrons: 11 Na 23 11
Rhenium Protons: 75 Neutrons: 111 Electrons: 75 Re 186 75
Rhenium isotope Protons: 75 Neutrons: 112 Electrons: 75 Re 187 75
133 55 EXAMPLE How many protons, neutrons and electrons are found in an atom of Cs Atomic number = protons /electrons There are 55 protons and 55 electrons Mass number = sum of protons and neutrons 133 – 55 = 78 There are 78 neutrons