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The ATOM By convention there is color, By convention sweetness, By convention bitterness, But in reality there are atoms and space. - Democritus (c. 400 BCE). Mass Number. Atomic Structure . ATOM. NUCLEUS. ELECTRONS. NEUTRONS. PROTONS. NEGATIVE CHARGE. POSITIVE CHARGE. NEUTRAL CHARGE.
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The ATOM • By convention there is color,By convention sweetness,By convention bitterness,But in reality there are atoms and space. • -Democritus (c. 400 BCE)
Mass Number Atomic Structure ATOM NUCLEUS ELECTRONS NEUTRONS PROTONS NEGATIVE CHARGE POSITIVE CHARGE NEUTRALCHARGE Atomic Number equals the # of...
Atomic Mass Units atomic mass unit (amu) = the mass of one proton 1.66 10-27 g
Mass Number Sum of the protons and neutrons in the nucleus of an atom Always a whole number # of neutrons = mass # - atomic # AtomicNumber The number of protons within the nucleus
Mass # Atomic# Isotopes Atoms of the same element with different numbers of neutrons Isotope symbol: 6 C “Carbon-12”
Atomic mass is an average • How to calculate the average atomic mass of an element: • List all isotopes,mass numbers, and percent relative abundance of an element • Multiply the mass number of each isotope by its relative abundance • Add all the products together = atomic mass
An example: • Chlorine-35 (35Cl) has 17 protons and 18 neutrons and has a relative abundance of 75.8% • Chlorine-37 (37Cl) has 17 protons and 20 neutrons and appears 24.2% of the time. • Multiply the mass number of each isotope by its relative abundance • (Chlorine-35) 35 amu× 0.758 = 26.53 amu • (Chlorine-37) 37 amu× 0.242 = 8.95 amu • Add all the products together = atomic mass • 26.53 amu + 8.95 amu = 35.48 amu