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How Atoms Differ

How Atoms Differ. What are the subatomic particles? What are their charges? Where are they located? What are their sizes?. 2. Properties of Subatomic Particles. What makes a carbon atom a carbon atom? What number represents the number of protons? How do we use the atomic number?.

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How Atoms Differ

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  1. How Atoms Differ

  2. What are the subatomic particles? • What are their charges? • Where are they located? • What are their sizes? 2

  3. Properties of Subatomic Particles

  4. What makes a carbon atom a carbon atom? • What number represents the number of protons? • How do we use the atomic number?

  5. Atomic Number • The atomic number is the number of protons or electrons in a neutral atom • Remember that atoms are neutral thus: • Atomic number = Number of protons = number of electrons • Each element has a unique number of protons • The periodic table is organized by increasing atomic number (number of protons) • Only protons determine the type of atom present and will never change for an element.

  6. Question Time • What does the atomic number represent? • Why are there an equal number of protons and electrons in a neutral atom? • How many protons and electrons are in aluminum (Al)? • An atom contains 28 protons, what element is it? How many electrons does it have? • How is the periodic table organized? • What subatomic particle determines the type of element?

  7. What is something that can be different from one atom of the same element to the next? • How would we figure out the mass of an atom? 8

  8. Isotopes and Mass Number What could isotope mean? Do you know any other words that begin with iso-? • Isotopes are atoms of the same element that have the same number of protons but different number of neutrons • Mass number represents the sum of the number of protons and neutrons in the nucleus • So, # of neutrons = mass number – atomic number

  9. Representing Isotopes • In Ag-107, the 107 represents the mass number (neutrons + protons) • In Ag-109, the 109 represents the mass number (neutrons + protons) How many neutrons are there?

  10. Question Time • What are isotopes? • What is the mass number? • What is the mass number in carbon-14? • What is the mass number and atomic number in Fe? • How many protons, neutrons, and electrons are in potassium-41, whose symbol is K? • How many protons, electrons, and neutrons are in Ne? • What is the difference between hydrogen ( H), deuterium ( H), and tritium ( H)? 56 26 22 10 1 1 3 1 2 1

  11. Could we use grams to measure the mass of an atom? • What could we use? • If there are multiple isotopes, how would we figure out the mass for the element?

  12. Atomic Mass • The mass of an atom is so small it is difficult to work with, so chemists have developed an atomic standard to compare all the masses to • The standard is the atomic mass unit (amu) is defined as 1/12 of the mass of a carbon-12 atom • If the mass of an element is not close to a whole number, it is because the atom has several isotopes • The atomic mass is the weighted average of the isotopes of that element.

  13. Example • Silver has two naturally occurring isotopes. Ag-107 has an abundance of 51.82% and mass of 106.9 amu. Ag-109 has a relative abundance of 48.18% and a mass of 108.9 amu. Calculate the atomic mass of silver.

  14. Question Time • Rubidium is a soft, silvery-white metal that has two common isotopes, Rb and Rb. If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium? 87 37 85 37

  15. Vocabulary to Know • Atomic #- • Mass #- • Isotopes- D. Atomic mass- same # of protons & electrons protons + neutrons written 2 ways: Carbon-14 or C 14 6 same # of protons, different # of neutrons weighted average mass

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