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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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Groups

Groups

Groups

periods Metals

Non Metals

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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 charge

Ca 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-anions

Nitrogen 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. Mono

2. Di

3. Tri

4. Tetra

5. Penta

6. Hexa

7. Hepta

8. Octa

9. Nona

10. deca

SF6

N2O5

CO

Sulfur Dioxide

PCl5

Phosphorus Trichloride

H2O

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Molecular compounds with common names

Formula Common

Name

Formula Common

Name

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 acid

NO3- is nitrate so HNO3 is

Nitric Acid -ite salt = -ous acid

NO2- is nitrite so HNO2 is

Nitrous Acid

HClO Hypoclorous Acid

HClO2 Chlorous Acid

HClO3 Chloric Acid

HClO4 Perchloric Acid