1. Atoms, Molecules, and Ions
Ch. 2 (cont.)

2. Note: Placement of elements 58 – 71 and 90 – 103 saves space
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3. Some important classifications:
A groups = representative elements or main group elements
I A = alkali metals
II A = alkaline earth metals
VII A = halogens
VIII = noble gases
B groups = transition elements
Inner transition elements = elements 58 – 71 and 90 – 103
58 – 71 = lanthanide elements
90 – 103 = actinide elements
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4. Metals, nonmetals, and metalloids
Note: groups IIIA-VIA contain all 3 classifications
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5. Metals Nonmetals Metalloids Tend to shine (have metallic luster)
Can be hammered or rolled into thin sheets (malleable) and can be drawn into wire (ductile)
Are solids at room temperature (except for Hg)
Conduct heat & electricity
Form alloys
Nonmetals
Lack the properties of metals
Exception: graphite form of carbon conducts electricity
React with metals to form (ionic) compounds
React with other nonmetals to form molecular (covalent) compounds
May be solid, liquid, or gas
Metalloids
Have properties between metals and nonmetals
Conduct electricity but not as well as metals (semiconductors)
Most elements are metals, slightly over a dozen are nonmetals,
and only a handful are metalloids.
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6. Tungsten (W)- a metal greyish-white lustrous metal
solid at room temperature
highest melting point (3400°C) and lowest vapor pressure of all metals
at temperatures over 1650°C has the highest tensile strength
used as filaments that glow white-hot in electric light bulbs
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7. Carbon (C)- a nonmetal
diamond
graphite
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8. Silicon (Si)- a metalloid
Being able to switch electrical conductivity “on” and “off” is the basis of a transistor
Solid state electronics
Computers, stereos, TV receivers, VCRs, CD players, and AM-FM radios rely on transistors made from semiconductors
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9. Group 1A – Alkali Metals
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10. Group 1A – Alkali Metals Properties: VERY REACTIVE
Na in water
Properties:
VERY REACTIVE
- never found free in nature
- react with water to form H2 and alkaline solution
- react with halogens (e.g. X = chlorine) to produce MX (e.g. NaCl)
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11. Group 2A – Alkaline Earth Metals
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12. Group 2A – Alkaline Earth Metals
Properties:
VERY REACTIVE
- never found free in nature
- react with water to form H2 and alkaline solutions (except Be)
- react with oxygen to form MO
- react with halogens (e.g. chlorine) to produce MX2 (e.g. MgCl2)
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13. Group 3A
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14. Group 3A Properties: 1 metalloid (boron) and 4 metals
- react with oxygen to form M2O3
- react with halogens (e.g. chlorine) to produce MX3 (e.g. BCl3)
- Al is most abundant metal in the earth’s crust
Bauxite, Al2O3
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15. Group 4A
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16. Group 4A 1 non-metal, 2 metalloids, 2 metals
- react with oxygen to form XO2 (e.g. CO2)
- carbon is the basis for organic and biochemistry
- Si common in minerals and used in microelectronics
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17. Group 5A
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18. Group 5A - 2 non-metals, 2 metalloids, 1 metal
- react with oxygen to form oxides
- nitrogen is 80% atmosphere
- N and P important in living organisms
- As is a poison
- Bi is heaviest non-radioactive element; used in PeptoBismol
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19. Group 6A – The Chalcogens
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20. Group 6A – The Chalcogens
- 3 non-metals, 1 metalloid, 1 metal
- highly reactive
- react with oxygen to form XO2 and XO3
- oxygen is 20% atmosphere and is involved in most biological energy sources
- S and Se are poisonous but need trace amounts for life
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21. Group 7A – the Halogens
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22. Group 7A – the Halogens All non-metals
Highly reactive… react with alkali metals to produce salts like NaCl
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23. Group 8A –The Noble Gases
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24. Group 8A – The Noble Gases
- least reactive elements
- not that abundant on earth
- after H, He is the most abundant element in the universe
- ‘neon’ signs
- Lighter than air balloons
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25. Group B – Transition Metals
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26. Group B – Transition Metals
all metals
wide variety of chemical reactivity
seldom found free in nature; except Ag, Au, Pt.
important commercial materials
includes lanthanides and actinides (e.g., U)
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27. Compounds Essentially all elements combine to form compounds
Compounds are of two types:
Molecular, which involve shared electrons and consist of electrically neutral, discrete particles called molecules
Ionic compounds, which involve electron transfer and charged particles called ions, do not exist as discrete molecular units
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28. Chemical formulas are collections of chemical symbols that are used to describe elements and compounds
Free elements are not combined with other elements in a compound
Fe (iron), Na (sodium), and K (potassium)
Many nonmetals occur as diatomic molecules
H2, N2, O2, F2, Cl2, Br2, I2
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29. Phosphorus, P4
Sulfur, S8
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30. Chemical formulas specify the composition of a substance
NaCl is composed of the elements sodium and chlorine in a one-to-one (atom) ratio
Fe2O3 is composed of the elements iron and oxygen in a two-to-three ratio
CO(NH2)2 expands to CON2H4, but there are good reasons to write some compounds with parentheses
Hydrates are crystals that contain water molecules, for example plaster: CaSO4 • 2H2O
When all the water is removed (by heating), the solid that remains is said to be anhydrous (without water)
When to use subscripts, parentheses, and dots
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31. Terminology Elements Compounds Molecular Ionic Acids Bases
Free elements
Diatomics
P4 and S8
Compounds
Molecular
Ionic
Acids
Bases
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32. A diatomic molecule contains only two atoms
A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds H2
H2O
NH3
CH4
A diatomic molecule contains only two atoms
H2, N2, O2, Br2, HCl, CO
A polyatomic molecule contains more than two atoms
O3, H2O, NH3, CH4
2.5
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33. cation – ion with a positive charge
An ion is an atom, or group of atoms, that has a net positive or negative charge.
cation – ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation. Na
11 protons
11 electrons
Na+
11 protons
10 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.
Cl-
17 protons
18 electrons Cl
17 protons
17 electrons
2.5
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34. A monatomic ion contains only one atom
Na+, Cl-, Ca2+, O2-, Al3+, N3-
A polyatomic ion contains more than one atom
OH-, CN-, NH4+, NO3-
2.5
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35. How many protons and electrons are in
Do You Understand Ions?
How many protons and electrons are in Al 27 13 ? 3+
13 protons, 10 (13 – 3) electrons
How many protons and electrons are in Se 78 34 2- ?
34 protons, 36 (34 + 2) electrons
2.5
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36. Common monoatomic ions
2.5
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