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ATOMIC STRUCTURE

ATOMIC STRUCTURE. ESSENTIAL QUESTION…. How can you identify an element and/or isotope based on its subatomic particles?. COMPOSED OF THREE SUBATOMIC PARTICLES: PROTON ( POSITIVELY CHARGED) NEUTRON ( NO CHARGE ) ELECTRON ( NEGATIVELY CHARGED). What is an atom composed of?.

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ATOMIC STRUCTURE

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  1. ATOMIC STRUCTURE

  2. ESSENTIAL QUESTION….. How can you identify an element and/or isotope based on its subatomic particles?

  3. COMPOSED OF THREE SUBATOMIC PARTICLES: • PROTON (POSITIVELY CHARGED) • NEUTRON (NOCHARGE) • ELECTRON (NEGATIVELY CHARGED) What is an atom composed of? BOTH IN THE NUCLEUS ALL FOUND OUTSIDE THE NUCLEUS (ELECTRON CLOUD)

  4. PROTONS (p+) • Proton is nearly 2000 times more massive than the electron, but equal in charge and opposite in sign to the electron • Number of protons in the nucleus is electrically balanced by an equal number of electrons • NEUTRONS (n0) • Massalmost exactly equal to that of the proton • ELECTRONS (e-) • Mass of electron much lessthanthe mass of a proton and neutron • Equal number of protons and electrons = NEUTRAL ATOM ABOUT THE PARTICLES…..

  5. ATOMIC NUMBER • REPRESENTS THE NUMBER OF PROTONS IN AN ATOM • ELEMENTS ARRANGED BY INCREASING ATOMIC NUMBER • UNIQUE TO A GIVEN ELEMENT • SINCE ALL ATOMS ARE NEUTRAL, ATOMIC NUMBER ALSO TELLS US THE NUMBER OF ELECTRONS IN AN ATOM • USUALLY FOUND AT THE TOP OF THE ELEMENT’S SYMBOL

  6. State the number of protons for atoms of each of the following: A. Nitrogen (N) 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur (S) 1) 32 protons 2) 16 protons 3) 6 protons C. Barium (Ba) 1) 137 protons 2) 81 protons 3) 56 protons Learning Check 1 LecturePLUS Timberlake

  7. MASS NUMBER • THE TOTAL NUMBER OF PROTONS AND NEUTRONS IN THE NUCLEUS OF AN ATOM • MASS NUMBER – ATOMIC NUMBER = # NEUTRONS • ROUND THIS NUMBER TO THE NEXT WHOLE NUMBER TODETERMINE THE MASS NUMBER Example: Sodium (Na) Mass Number = 23 Atomic Number = 11 ______ 12 neutrons -

  8. Practice From the Periodic Table Complete the following chart:

  9. DALTON THOUGHT THAT….. • Atoms could not be divided(indivisible)….atoms can be divided • All atoms of an element are IDENTICAL….not really!! • Atoms of an element have same number of p+ and e-, but the number of n0 may be different ISOTOPES

  10. ISOTOPES ARE… • Atoms of the same element with the same number of protons, but different numbers of neutrons. • Atoms of the same element (same atomic number) with different mass numbers ISOTOPES

  11. THE ISOTOPES OF HYDROGEN All atoms have the same number of protons (p+=1)……. ….but different number of neutrons in the nucleus (which means these isotopes will have different mass numbers!!)

  12. A Z X A= mass number (the total number of protons + neutrons) Z= atomic number (the total number of protons) X= element symbol ISOTOPIC NOTATION

  13. 46 21 Sc 46 = mass number (the total number of protons (21) + neutrons (25)) 21 = atomic number (the total number of protons (21)) Sc= element symbol (In a neutral atom, the number of electrons (21) is equal to the number of protons) READING ISOTOPIC NOTATION

  14. 46 21 Sc or Scandium-46 Name of the element followed by the mass number (This format does not include the atomic number) Another way of writing an isotope

  15. 1631 65 O PZn 81530 8 p+ 15 p+ 30 p+ 8 n 16 n 35 n 8 e- 15e- 30 e- Practice LecturePLUS Timberlake

  16. An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is 1) 14 2) 16 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 practice LecturePLUS Timberlake

  17. Most elements found as a mixture of isotopes • Relative abundance of each isotope is constant • Example: Potassium in bananas • 93.25% of K atoms have 20 n0 • 6.7302% of K atoms have 22 n0 • 0.0117% of K atoms have 21 n0 Isotopes LecturePLUS Timberlake

  18. Isotopes of an element differ in mass • The more neutrons in an isotope, the greater the mass • Still, isotopes of an element have the same chemical behavior • Why? Chemical behavior depends on the number of e-, not n0 or p+ Isotopes LecturePLUS Timberlake

  19. Percent abundance of isotopes Mass of each isotope of that element Average Atomic Mass= mass isotope1(percent abundance1)+ mass isotope2(percent abundance2)+ … 100 100 Calculating Atomic Mass LecturePLUS Timberlake

  20. Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% 25Mg = 25.0 amu 10.13% 26Mg = 26.0 amu 11.17% Average atomic mass of Mg = 24.3 amu Atomic Mass of Magnesium Mg 24.3 LecturePLUS Timberlake

  21. Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the atomic mass of gallium? Learning Check AT7 LecturePLUS Timberlake

  22. Ga-69 (%/100) 68.9 amu x 60.2 = 41.5 amu for Gallium-69 100 Ga-71 (%/100) 70.9 amu x 39.8 = 28.2 amu for Gallium-71 100 Atomic mass Ga = 69.7 amu Solution AT7 LecturePLUS Timberlake

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