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Masses of Atoms

Masses of Atoms. Atomic mass. Nucleus contains most of the mass of the atom Protons and neutrons are far more massive than electrons Mass of a proton or neutron is approximately 1.6726 X 10 -24 This mass of a proton is about 1,836 times the mass of an electron. Mass of atomic particles.

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Masses of Atoms

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  1. Masses of Atoms

  2. Atomic mass • Nucleus contains most of the mass of the atom • Protons and neutrons are far more massive than electrons • Mass of a proton or neutron is approximately 1.6726 X 10-24 • This mass of a proton is about 1,836 times the mass of an electron

  3. Mass of atomic particles • Not measured in normal units • Amu – atomic mass unit

  4. Protons Identify the Element • Each element can be described by the number of protons it has • The number of protons in an atom is known as its atomic number • What is the atomic number for the following atoms??? • Nitrogen (N), Oxygen (O), Hydrogen (H), Boron (B), Silver (Ag), Antimony (Sb)

  5. Identifying an Element • If we know one of the following we then know also the other two: • Atomic number • Name of the element • Number of protons

  6. Mass number • The mass number of an atom is the sum of the number of protons and the number of neutrons in the nucleus of an atom. • Mass number

  7. Neutrons in an atom • By using the atomic number and the mass number (which is also called the atomic mass) you can find how many neutrons are in an atom of an element. • Number of neutrons = mass number – atomic number

  8. Differing number of Neutrons • Some elements can be found with differing number of neutrons • Isotopes – atoms of the same element that have different numbers of neutrons • Some elements such as Carbon have different Isotopes there is a Carbon-12 isotope and a Carbon-14 isotope… which means that Carbon-12 isotope has 12 neutrons and Carbon-14 isotope has 14 neutrons

  9. Atomic mass number • Decimal places are found in the mass number… this is because the mass number is the average atomic mass of an element • Average atomic mass – the weighted-average mass of the mixture of its isotopes • For example • If we had 5 boron atoms randomly found in nature • 4 Boron-11 and 1 Boron-10 • How would we find the average atomic mass of these atoms??? • The average atomic mass of boron is close to the mass of its most abundant isotope, boron-11

  10. Draw a diagram • On a blank sheet of paper please draw a diagram for the nucleus of each of the following: Carbon-12, Carbon-13, and Carbon-14. And Identify which Carbon Isotope is found more often (hint you can calculate this or it is in your book). • Be sure to put the correct amount of protons and neutrons (using different colors) – also write underneath how many protons and neutrons for each isotope. • Correctly label each isotope and color coordinate your protons and neutrons (place a key in the corner to correctly identify which are protons and which are neutrons). • An example of how to draw a nucleus is Figure 8 on page 515. • At the bottom of the page explain what an isotope is • and reference your drawing.

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