1. Introduction to Chemistry for Allied Health Sciences Structure of the Atom Kirk Hunter Chemical Technology Department Texas State Technical College Waco

2. Structure of the Atom

3. Subatomic Particles NameRelative Relative Mass (amu) Charge Proton1+1 Neutron1 0 Electron0-1

4. ATOM The protons and neutrons are located in the center in the region called the nucleus.

5. ATOM Electrons are found around the nucleus in shells or principle energy levels (PEL).

6. ATOMIC NUMBER The number of protons in the nucleus of an atom Z = #p

7. ATOMIC NUMBER For a neutral atom, the number of protons is equal to the number of electrons. #p = #e

8. MASS NUMBER The sum of protons and neutrons in the nucleus of an atom. A = #p + #n

9. MASS NUMBER Round the atomic weight to the nearest whole number ElementAtomic MassMass Number Li6.941 Ca40.078 B10.81 Au196.9665 7 41 11 197

10. Isotopic Notation A = mass number E = symbol of element Z = atomic number E A Z

11. Isotopic Notation Example: Determine the number of protons, electrons and neutrons in 51 23 V.

12. Isotopic Notation Example: Determine the number of protons, electrons and neutrons in 51 23 V. Solution: # p = 23 # e - = 23 # n = 51 - 23 = 28

13. Isotopic Notation Example: Determine the number of protons, electrons and neutrons for the following: 14 7 N 238 92 U 23 11 Na 200 80 Hg

14. Isotopic Notation Example: Determine the number of protons, electrons and neutrons for the following: 14 7 N 238 92 U 23 11 Na 200 80 Hg #p #e - #n 777777 92 146 11 12 80 120

15. Isotopes Around 20 elements have a fixed number of neutrons. Atoms of the same element having a different number of neutrons are called isotopes. Isotopes have the same number of protons and a different number of neutrons.

16. Isotopes of Hydrogen 1 1 H 2 1 H 3 1 H Protium Deuterium Tritium p + 1 1 1 n 0 0 1 2 e - 1 1 1

17. Isotopes of Helium 3 2 He 4 2 He p + 2 2 n 0 1 2 e - 2 2

18. Isotopes of Oxygen 16 8 O 17 8 O 18 8 O p + 8 8 8 n 0 8 9 10 e - 8 8 8

19. ATOMIC MASS UNIT Carbon-12 used as the reference standard. All atoms are compared to C-12. 1 amu = 1/12 the mass of a C-12 atom.

20. ATOMIC MASS The average mass of all isotopes of the element. –exact mass of each isotope –percent abundance of each isotope in nature

21. ATOMIC MASS Example: Determine atomic mass of vanadium. Isotopeexact mass% abundance 51 V50.9876 amu 35.64% 52 V51.9346 amu 64.36% At.wt.=(50.9876 *0.3564) + (51.9346 * 0.6436) = 18.17+33.43 = 51.60 amu

22. ATOMIC MASS Example: Determine atomic mass of silicon. Isotopeexact mass% abundance 26 Si25.9854 amu5.435% 28 Si27.9721 amu76.42% 29 Si28.9632 amu18.15% At.wt. = (25.9854*0.05435)+(27.9721*0.7642) +(28.9632*0.1815) = 28.05 amu