1. CHEMISTRY of the Atom

2. The particle is said to “hold” atoms together in molecules.
CHEMISTRY of the Atom
PARTICLES:
Mass Charge Symbol
Nucleus:
PROTON amu H+, H, p
NEUTRON amu n
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ELECTRON very small e -
The particle is said to “hold” atoms together in molecules.
© Copyright R.J. Rusay

3. Periodic Table Mendeleev’s Table 1868-1871
Mural at St.Petersburg University, Russia
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4. Periodic Table Elements are classified by:
- properties & atomic number
- metals, non-metals, metalloids
Groups or Families (vertical)
1A = alkali metals
2A = alkaline earth metals
7A = halogens
8A = noble gases
Periods (horizontal)

5. Group 1 and Group 2 Metals

6. Modern Periodic Table From Los Alamos National laboratory:
© Copyright 1998 R.J. Rusay

7. Using the Periodic Table

8. Atoms, Molecules & Ions Atoms: # Protons = Atomic Number
Atomic Mass = # Protons + # of Neutrons
Isotope: same atomic number but different atomic mass
Periodic Table atomic mass is a weighted average of isotopic masses
© Copyright R.J. Rusay

9. Atoms, Molecules & Ions Atomic Mass of Carbon:
What is the “weighted” atomic mass?
© Copyright R.J. Rusay

10. Atoms, Molecules and Ions
Atomic Number = 6 (atom’s identity)
Carbon
Atomic Mass = 13 (isotope 13)
6 protons; # neutrons =
neutral atom has 6 electrons
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11. Atomic Symbols 39 K
Mass number 
 Element Symbol 19
Atomic number 

12. Atoms, Molecules and Ions
Atomic Number = 12 (atom’s identity)
Atomic Mass = 24
12 protons; # neutrons =
neutral atom has 12 electrons
Ion contains 10 electrons: symbol?
12 p e- = +2
© Copyright R.J. Rusay

13. Atoms, Molecules and Ions
Atomic Number = 17 (atom’s identity)
Atomic Mass = ?
# protons = ? ; # neutrons = ?
neutral atom has ? electrons
Ion contains 18 electrons: symbol?
17 p e- = -1
© Copyright R.J. Rusay

14. Ions Cation: A positive ion Mg2+, NH4+ Anion: A negative ion
Cl, SO42
Ionic Bonding: Force of attraction between oppositely charged ions.

15. Molecules Neutrally Charged Eg. Salt: NaCl -> 1 Na+ and 1 Cl -
What is the proportion of ions for a compound formed from Mg ion and chlorine?
Mg2+ and Cl
1 Mg2+ combines with 2 Cl

16. C20H26N2O (Ibogaine, not ionic)
Chemical Formulas
Molecular Formula:
Elements’ Symbols = atoms
Subscripts = relative numbers of atoms
How many atoms of each element are in the following componds?
MgCl2 CCl4 NaOH (NH4) 2CO3
C20H26N2O (Ibogaine, not ionic)