1. Chapter 3 Atoms and Elements
The Atom
Atomic Number and Mass Number
Ions & Isotopes

2. Atomic Theory Atoms are building blocks of elements
Similar atoms in each element
Different from atoms of other elements
Two or more different atoms bond together
to form compounds

3. History of the atom Not the history of atom, but the idea of the atom
Original idea Ancient Greece (400 B.C..)
Democritus Greek philosopher

4. Hyle Another Greek Aristotle - Famous philosopher
All substances are made of 4 elements
Fire - Hot
Air - light
Earth - cool, heavy
Water - wet
Blend these in different proportions to get all substances
Hyle

5. . e-
nucleus

6. Who’s Next? Late 1700’s - John Dalton- England
Teacher- summarized results of his experiments and those of other’s
In Dalton’s Atomic Theory
Combined ideas of elements with that of atoms

7. Dalton’s Atomic Theory
All matter is made of tiny indivisible particles called atoms.
Atoms of the same element are identical, those of different atoms are different.
Atoms of different elements combine in whole number ratios to form compounds
Chemical reactions involve the rearrangement of atoms. No new atoms are created or destroyed.

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

9. Subatomic particles Actual mass (g) Relative mass Name Symbol Charge
Electron e- -1
9.11 x 10-28
1/1840
Proton p+ +1
1.67 x 10-24 1
Neutron n0
1.67 x 10-24 1

10. Subatomic particles Relative mass Name Symbol Charge Electron e- -1
Mass (amu)
Name
Symbol
Charge
Electron e- -1
1/1840
Proton p+ +1 1 1 1
Neutron n0 1

11. Subatomic Particles Particle Symbol Charge Relative Mass
Electron e
Proton p
Neutron n

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

13. Atomic Number on the Periodic Table11 Na
Atomic Number
Symbol

14. All atoms of an element have the same number of protons11 Na
11 protons
Sodium

15. Learning Check
State the number of protons for atoms of each of the following:
A. Nitrogen
B. Sulfur
C. Barium

16. Solution
State the number of protons for atoms of each of the following:
A. Nitrogen
7 protons
B. Sulfur
16 protons
C. Barium
56 protons

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

18. All atoms of an element have the same number of protons and electrons11 Na
11 protons
11 electrons
Sodium

19. Atomic Mass
Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom.

20. Atomic Mass on the Periodic Table11 Na
Atomic Number
Symbol
Atomic Mass

21. Atomic Mass on the Periodic Table11 Na
Atomic Number
Symbol
Mass # 23
Atomic Mass

22. Mass Number Determined by : the whole Number closest
to the atomic mass
Counts the number of protons and neutrons
in an atom

23. Atomic Symbols atomic number Show the mass number and atomic number
Give the symbol of the element
mass number
Na sodium-23
atomic number 23 11

24. Subatomic Particles in Some Atoms
O P Zn 16 65 31 15 30 8
8 p p p+
8 n 16 n 35 n
8 e e e-

25. 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
chlorine chlorine - 37

26. Naturally occurring hydrogen consists of three isotopes, protium (H-1),deuterium (H-2), and tritium (H-3). State the number of protons, neutrons, and electrons in each of these atoms.
1H H 3H
#p _______ _______ _______
#n _______ _______ _______
#e _______ _______ _______ 1 1 1

27. Naturally occurring hydrogen consists of three isotopes,
protium deuterium tritium
1H H 3H #p #e #n 1 1 1

28. An atom of zinc - ( Zn-65)
A. Number of protons in the zinc atom
B. Number of neutrons in the zinc atom
C. What is the mass number of a zinc isotope
with 37 neutrons?

29. An atom of zinc - ( Zn-65) A. Number of protons in the zinc atom 1) 30
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

30. 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 ___________

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

32. IONS Na Cl Atoms with a charge (positive or negative)
Atoms which gain or lose an electron
atom ion #p #e #p #e 1+ Na 1- Cl

33. IONS
atom ion #p #e #p #e 2+ Mg 2- O

34. Complete Atomic Symbol combines isotopes and ionsAl
Mass # 27 3+
Ionic charge
Atomic # 13
13p e n

35. Learning Check N P Zn 14 3- 65 2+ 32 3- 15 30 7 7p+ 15 p+ 30 p+
7n 17 n 35 n
10e e e-

36. Example of an Average Atomic Mass
Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine.
35 x =
100
35.5
37 x =