The Atom Atomic Number and Mass, Isotopes

1. The Atom Atomic Number and Mass, Isotopes

2. Elements • Pure substances that cannot be separated into different substances by ordinary processes • Are the building blocks of matter • 112 elements known today Examples: carbon gold calcium

3. Symbols of Elements • Use 1 or 2 letter abbreviations • Capitalize the first letter only Examples: C carbon Co cobalt N nitrogen Ca calcium F fluorine Br bromine O oxygen Mg magnesium

4. Symbols from Latin Names Element Symbol Latin name Copper Cu cuprum Gold Au aurum Lead Pb plumbum Mercury Hg hydrargyrum Potassium K kalium Silver Ag argentum Sodium Na natrium Tin Sn stannum

5. % Major Elements in the Body O 65.0 % K 0.34 C 18.0 S 0.26 H 10.0 Na 0.14 N 3.0 Cl 0.14 Ca 1.4 Fe 0.004 P 1.0 Zn 0.003 Mg 0.50 Trace Elements As, Cr, Co, Cu, F, I, Mn, Mo, Ni, Se, Si, V

6. Learning Check Select the correct symbol for each: A. Calcium 1) C 2) Ca 3) CA B. Sulfur 1) S 2) Sl 3) Su C. Iron 1) Ir 2) FE 3) Fe

7. Solution Select the correct symbol for each: A. Calcium 2) Ca B. Sulfur 1) S C. Iron 3) Fe

8. Learning Check Select the correct name for each: A. N 1) neon 2) nitrogen 3) nickel B. P 1) potassium 2) phogiston 3) phosphorus C. Ag 1) silver 2) agean 3) gold

9. Solution Select the correct name for each: A. N 2) nitrogen B. P 3) phosphorus C. Ag 1) silver

10. Periodic Table • Represents physical and chemical behavior of elements • Arranges elements by increasing atomic number • Repeats similar properties in columns known as chemical families or groups

11. Subatomic Particles Particle Symbol Charge Relative Mass Electron e- 1- 0 Proton p+ + 1 Neutron n 0 1

12. Location of Subatomic Particles 10-13 cm electrons protons neutrons 10-8 cm nucleus

13. Atomic Number Counts the number of protons in an atom

14. Periodic Table 1 2 3 4 5 6 7 8 11 Na

15. Atomic Number on the Periodic Table 11 Na Atomic Number Symbol

16. All atoms of an element have the same number of protons 11 Na 11 protons Sodium

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

18. Solution AT 1 State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium 3) 56 protons

19. Number of Electrons • An atom is neutral • The net charge is zero • Number of protons = Number of electrons • Atomic number = Number of electrons

20. Mass Number Counts the number of protons and neutrons in an atom

21. Atomic Symbols • Show the mass number and atomic number • Give the symbol of the element mass number 23 Nasodium-23 atomic number11

22. More Atomic Symbols 16 31 65 O P Zn 8 15 30 8 p+ 15 p+ 30 p+ 8 n 16 n 35 n 8 e- 15e- 30 e-

23. Isotopes • Atoms with the same number of protons, but different numbers of neutrons. • Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35Cl 37Cl 1717 chlorine - 35 chlorine - 37

24. Learning Check AT 2 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 _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______

25. Solution AT 2 12C 13C 14C 6 6 6 #P __6____ 6___ ___6___ #N __6___ __7___ ___8___ #E __6____ 6___ ___6___

26. Learning Check AT 3 An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 2) 35 3) 65 B. Number of neutrons in the zinc atom 1) 30 2) 35 3) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67

27. Solution AT 3 An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 B. Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67

28. Learning Check AT 4 Write the atomic symbols for atoms with the following: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 47 e- ___________

29. Solution AT 4 16O A. 8 p+, 8 n, 8 e- 8 B. 17p+, 20n, 17e- 37Cl 17 C. 47p+, 60 n, 47 e- 107Ag 47

30. Learning Check AT 5 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

31. Solution AT 5 An atom has 14 protons and 20 neutrons. A. It has atomic number 1) 14 B. It has a mass number of 3) 34 C. The element is 1) Si D. Another isotope of this element would be 3) 36X 14

32. Masses of Atoms • A scale designed for atoms gives their small atomic masses in atomic mass units (amu) • An atom of 12C was assigned an exact mass of 12.00 amu • Relative masses of all other atoms was determined by comparing each to the mass of 12C • An atom twice as heavy has a mass of 24.00 amu. An atom half as heavy is 6.00 amu.

33. Atomic Mass Na 22.99 • Listed on the periodic table • Gives the mass of “average” atom of each element compared to 12C • Average atom based on all the isotopes and their abundance % • Atomic mass is not a whole number

34. Learning Check AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium __________ B. aluminum __________ C. lead __________ D. barium __________ E. iron __________

35. Solution AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium _40.1 amu _ B. aluminum _27.0 amu _ C. lead _207.2 amu_ D. barium _137.3 amu_ E. iron _55.8 amu__

36. Calculating Atomic Mass • Percent(%) abundance of isotopes • Mass of each isotope of that element • Weighted average = mass isotope1(%) + mass isotope2(%) + … 100100

37. Atomic Mass of Magnesium Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% 25Mg = 25.0 amu 10.13% 26Mg = 26.0 amu 11.17% Atomic mass (average mass) Mg = 24.3 amu Mg 24.3