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Atoms, Isotopes, & Ions

Atoms, Isotopes, & Ions. Electron cloud. Nucleus. The Structure of the Atom. An atom consists of a nucleus protons and neutrons electrons in orbitals around the nucleus. Atomic # = # of protons in an atom. Mass # = # of protons + neutrons in an atom. Atomic Number vs Mass Number. 4

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Atoms, Isotopes, & Ions

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  1. Atoms, Isotopes, & Ions

  2. Electron cloud Nucleus The Structure of the Atom An atom consists of a • nucleus • protonsand neutrons • electrons in orbitals around the nucleus.

  3. Atomic # = # of protons in an atom Mass # = # of protons + neutrons in an atom Atomic Number vs Mass Number 4 2 Mass Number  Atomic Number  He

  4. 11B 10B Isotopes • Isotopes - Atoms of the same element but different mass number. • Boron-10 (10B) has 5 p and 5 n • Boron-11 (11B) has 5 p and 6 n

  5. Isotopes? Which of the following represent isotopes of the same element? Which element? 234 X234 X235 X238 X 92939292

  6. Isotopes & Their Uses Bone scans with radioactive technetium-99.

  7. Isotopes & Their Uses The tritium content of ground water is used to discover the source of the water, for example, in municipal water or the source of the steam from a volcano.

  8. Counting Protons, Neutrons, and Electrons • Protons: Atomic Number (from periodic table) • Neutrons: Mass Number minus the number of protons (mass number = protons +neutrons) • Electrons: • If it’s an atom, the protons and electrons must be the SAME so that it is has a net charge of zero (equal numbers of + and - charges) • If it does NOT have an equal number of protons & electrons, it is NOT an atom, it is an ION.

  9. Learning Check Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 13C 14C 6 6 6 #p+ _______ _______ _______ #no _______ _______ _______ #e- _______ _______ _______

  10. Answers 12C 13C 14C 6 6 6 #p+666 #no678 #e- 6 66

  11. IONS • IONSare atoms or groups of atoms with a positive or negative charge. • Taking away an electron from an atom gives it a positive charge. • Adding an electron to an atom gives it anegative charge. • To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2 Na Ca I O

  12. Forming Cations & Anions An ANION forms when an atom gains one or more electrons and therefore has an overall negative charge. A CATION forms when an atom loses one or more electrons and therefore has an overall positive charge.

  13. QUESTIONS • What is the result when the number of electrons for a given atom changes? • What is the result when the number of neutrons for a given atom changes? • What is the result when the number of protons for a given atom changes?

  14. Learning Check An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 20 3) 34 B. Its mass number is 1) 14 2) 20 3) 34 C. The element is 1) Si 2) Ca 3) Se D. Another isotope of this element is 1) 34X 2) 34X 3) 36X 16 14 14

  15. Visualizing Isotopes & Ions • Hydrogen Ion: http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-ions.shtml • Hydrogen Isotope: http://web.visionlearning.com/custom/chemistry/animations/CHE1.3-an-isotopes.shtml

  16. Learning Check State the number of protons, neutrons, and electrons in each of these ions. 39 K+16O -241Ca +2 19 8 20 #p+ ______ ______ _______ #no ______ ______ _______ #e- ______ ______ _______

  17. One Last Learning Check Write the nuclear symbol form for the following atoms or ions: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 46 e- ___________

  18. Isotopes and Average Atomic Mass • A sample of any element consists of one or more isotopes of that element. • Each isotope is a different weight. • The relative amounts of each isotope for any element represents the isotope distribution for that element. • The atomic weight is the average of the isotope weights weighted for the isotope distribution Atomic Mass =[(mass of isotope) (%abundance) ] + [(mass of isotope) (%abundance)] + [….] 100%

  19. Practice Problem • The natural abundance for boron isotopes is: 19.9% 10B (10.013 amu) and 80.1% 11B (11.009amu). Calculate the atomic weight of boron. 

  20. Some Humor A neutron walks into a restaurant and orders a couple of drinks. As she is about to leave, she asks the waiter how much she owes. The waiter replies, “For you, No Charge!!!”

  21. Next week…how does atomic structure relate to the periodic table?

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