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Chapter 2 Atoms, Molecules, and Ions
1. Atoms and the atomic theory2. Components of the atom3. The periodic table4. Molecules and Ions5. Ionic Formulas6. Names of Compounds
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Atoms and the Atomic Theory
Elements consist of tiny particles called atoms.Atoms retain their identity in reactions.In a compound, atoms combine in fixed ratios of
small whole numbers. ( Water = 2 H, 1 O )
Key Figures: Rutherford Discovered nucleus [Gold foil
experiment] JJ Thompson
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Thomson’s discovery of the electron
Negatively charged Smaller than proton (1/2000) 0.005
AMU
Electrons
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Components of Atoms
Relative mass Relative charge Location
Proton 1 +1 Nucleus
Neutron 1 0 Nucleus
Electron 0.0005 -1 Electron cloud
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Atomic Number, Mass Number
Atomic Number = # of protons in nucleus = # of electrons in a neutral atom. (not an ion)
Atomic Numberis characteristic of a particular element. (all Hydrogen atoms have 1, Helium 2)
Mass Number discovery of the nucleus
= # of protons + # of neutrons
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Isotopes:Atoms of the same element with a different mass number.
Protons Neutrons Atomic Number
Nuclear Symbol
Mass Number
Carbon-12 6 6 6 12
Carbon-14 6 8
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Isotopes of Hydrogen
No neutrons 1 neutron 2 neutrons
deuterium tritiumprotium
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Nuclear stability(stable isotopes)
Small elements (Up to atomic # 20) the stable proton:neutron ratio = 1:1 Carbon 12, C-12 is a
stable carbon isotope. C-16 is unstable.
After element 20…Then more neutrons are
needed to mute the repulsive force of the protons in the nucleus.
For heavy elements Atomic Number =80+ the stable P:N ratio is 1:1.5
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Molecules
Usually made up of non-metal atomsHeld together by covalent bonds
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Types of formulas
Using ethyl (drinking) alcohol as an example:
Molecular Formula: C2H6OGives # and type of each element
Structural Formula:Shows how atoms are bonded
Condensed Structural: CH3CH2OHGives structural hints
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Ions
Formation of monatomic ionsGain or lose in order to obtain a noble gas electron configuration.
Lose electrons: (metals)Na Na+ + e-
Gain electrons: (non-metals)F + e- F –
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Monatomic ion charges
Cations (+) Group 1 +1 Group 2 +2 Aluminum +3
Anions (-) Group 17 -1 Group 16 -2 Nitride -3
Find their locations on the periodic table and label them with their familiar names.
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Monatomic ions of Transition Metalsand POST-transition metals
Many are polyvalent i.e. multiple possible
charges. Fe2+, Fe3+
Cu+, Cu2+
Pb2+, Pb4+
Sn2+, Sn4+
Key monovalent ions: Silver Ag+
Zinc Zn2+
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Polyatomic Ions
Group of several atoms acting as an ionic unit. Ex. NO3 - Nitrate
NH4+ and Hg2
2+ are the only common polyatomic ions with a positive charge. (Cations)
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Determine if the following are ionic or molecular
KClNaNO3
CO2
PBr3
CoOCCl4
IonicIonicMolecularMolecularIonicMolecular
Ionic: metal and non metal (or polyatomic ion)
Molecular: 2 or more non metals
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Formulas of Compounds Ionic compounds:
Apply principle of electroneutrality.
Cation Anion Formula Net chargeCa 2+ F- CaF2
Al3+ NO3- Al(NO3)3
Na+ H2PO4- NaH2PO4
Zn2+ C2H3O2- Zn(C2H3O2)2
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Ionic Compounds dissolved in water: “electrolytes” Electrolytes can carry a current to complete a
circuit. Ionic compounds are electrolytes
They may be strong or weak.
Molecular compounds are non-electrolytes. They will NOT carry a current to complete a circuit.
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Names of compounds
Ionic: Join together the names of the 2 ions
Na+ (sodium) Br- (bromide)= NaBr = sodium bromide
Polyvalent transition metals include charge in the name
Fe3+ (Iron III) O2- (Oxide) = Fe2O3= Iron (III) Oxide
Oxo-anions -ate, -ite, per-, hypo-
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Systematic naming of oxo-anionsNitrogen Sulfur Chlorine Bromine Iodine
Hypo-(least)
x x Hypochlorite Hypo-bromite
Hypoiodide
-ite(less)
Nitrite Sulfite Chlorite Bromite Iodide
-ate(more)
Nitrate sulfate Chlorate Bromate Iodate
Per-(most)
x x perchlorate perbromate periodate
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Practice Naming
Na3N Cu(NO3)2
LiBrO2
LiF BeIO4
Sodium Nitride Copper (II) Nitrate Lithium Bromite Lithium Fluoride Beryllium Periodate
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Names of compounds
Molecular: Use greek prefixes to indicate # of atoms
1st element: Name + greek # if more than one.
2nd element: Greek # prefix + “ide” version of element name.
CO2 = Carbon Dioxide
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Greek Number Prefixes 1-10
1. Mono2. Di3. Tri4. Tetra5. Penta6. Hexa7. Hepta8. Octa9. Nona10. deca
SF6
N2O5
CO
Sulfur Dioxide
PCl5
Phosphorus Trichloride
H2O
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Molecular compounds with common names
Formula CommonName
Formula CommonName
H2O Water PH3Phosphine
H2O2Hydrogen Peroxide
AsH3Arsine
NH3Ammonia NO Nitric Oxide
N2H4Hydrazine(a rocket fuel)
N2O Nitrous Oxide(laughing gas)
C2H2Acetylene
(welding gas)CH4
Methane(natural gas)
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Acids Compounds with an “H” that ionizes in water. HCl, in water is an electrolyte of H+ and Cl- ions.
Acid namingBinary (2 types of atoms) use the “–ic” suffix
HCl Hydrochloric acid
HI Hyrodiodic acid
HBr Hyrdrobromic acid
HF Hyrdrofluoric acid
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Acids Oxo acids:
-ate salt = -ic acidNO3
- is nitrate so HNO3 is
Nitric Acid -ite salt = -ous acidNO2
- is nitrite so HNO2 is
Nitrous AcidHClO Hypoclorous AcidHClO2 Chlorous Acid
HClO3 Chloric Acid
HClO4 Perchloric Acid
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