The Periodic TableChapter 5

5.1 The periodic table Dimitri Mendeleev - publish first real periodic table -

1869 Based on chemical and physical properties Listed elements in increasing atomic mass order Left spaces for undiscovered elements His basic rule: the elements in any group, of the

table are similar to their column-mates. Ex, look at the first column on the left, underneath hydrogen (H). The elements in this group are the alkali metals; they're all soft metals that react violently with water to make hydrogen gas.

…… Periodic Table aluminum Ga(1875)

atomic mass 68 69.7

density 5.9 5.9

melting point low 29.8 Co

oxide formula Al2O3 Ga2O3

….. Periodic Table Mendeleev formulated the original Periodic Law -

Properties of elements are a periodic function of their atomic mass.

1911 - Mosely (English) discovers the proton so....new Periodic Law - Properties of elements are a periodic function of atomic number.

*** History lesson - After his brilliant discovery, Mosely was drafted into the infantry to fight for the crown in WW I. He was killed. Only after the war was it realized that scientists should probably not be drafted into combat roles. That policy exists to this day.***

5.2 Electron configurations and the periodic table *** valence e- have largest

effect on chemical/physical properties

Label the groups/ families and periods

s s

s s p p p p p p

s s p p p p p p

s s d d d d d d d d d d p p p p p p

s s d d d d d d d d d d p p p p p p

s s d d d d d d d d d d p p p p p p

s s

f f f f f f f f f f f f f f

f f f f f f f f f f f f f f

Names of Families Group 1 - Alkali Metals – They are not found alone in nature - why? explosive with

water - they are stored under kerosene - very reactive. They react with nonmetals to form salts. They are silvery, shiny (luster), have a low melting point, and

are soft (so soft, you can cut them with a knife). They are malleable (able to flattened into a sheet) and ductile

(able to be drawn into a wire). Sodium and Potassium are particularly important in body

chemistry.

…..Families Group 2 - Alkaline Earth Metals - 2nd most reactive elements. Also not “lone

state” elements. Harder, denser than group 1. Common in

sea salts.

…..Families Transition Metals - Groups 3-12. Harder, more brittle, higher melting point than groups 1 and 2. Form colored compounds. Conduct heat and electricity well and are shiny. Pd, Pt, Au - very unreactive (Noble metals). They can't be divided neatly into groups; all of them have very

similar properties. Their valence electrons vary in chemical reactions. E.x. Iron (Fe),

sometimes likes to give away 2e-, and sometimes 3e-.

…..Families Metalloids – B, Si, As, Te, At, Ge, Sb - stairs and 2 people under the

stairs. Properties of metals and nonmetals. Brittle - used in semiconductors, computers.

….. Families Halogens - Group VII / 17 – most reactive of the nonmetals. Not found free in nature. Solids, liquids, and gases in this group. Widespread - sea salts, minerals, living tissue. Many applications - bleach, photography, plastics,

insecticides.

….. Families Noble Gases - Group 18 – Least reactive elements - used in air conditioners, double pane windows, lights, balloons.

….. Families Lanthanides - f block rare earth elements (not really rare) - shiny, silver,

reactive, make TV’s glow. Some have very interesting properties. For example,

gadolinium (Gd) is the only rare earth that's ferromagnetic--that is, it sticks to magnets, the way iron does.

Lanthanum is the only superconductor among them; at very low temperatures, it loses all resistance to the flow of electricity.

….. Families Actinides - f block

unstable, radioactive - all but 4 are artificially created.

Side note - f block elements are called inner transition

elements - they were put into their current position by Glenn Seaborg - the only living person ever to have an element named after him.

5.3 Electron Configuration and Periodic Properties

Periodic Trends: For all of the following periodic trends you

should: know the definition be able to draw the trend on periodic table

drawings with arrows explain why the trend happens relate the trend to other trends apply the trends on an “AB” sheet

Periodic Trends 1. Atomic Radius - basic idea is “how big an atom is”

- atoms are not spheres with outer boundaries due to the wave mechanical model. 2 trends

size - natural, logical - add more shells

size - not logical! why? from left to right - more protons are added, but not

more shells. Higher charged nucleus pulls electrons closer.

Periodic Trends Atomic Radius

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Periodic Trends Atomic Radius

Examples Which has a larger radius?

Mg or Ca? F or B?

Periodic Trends 2. Electronegativity- basic idea - the ability

of an atom to attract electrons (Linus Pauling) Electronegativity is related to atomic size…. They

are opposites Trend

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Periodic Trends Electronegativity

Examples Which has a larger electronegativity?

Cs or Mg? Mn or F?

Periodic Trends 3. Ionization energy - energy required to remove the

most loosely held electron from the outer energy level of an atom. A(g) + energy yields A+(g) + e-

Trend:

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Periodic Trends IE is related to atomic radius - 2 reasons why smaller going down

the table

1. greater distance from the nucleus - less attraction

2. inner electrons “shield” outer electrons from the nucleus

Examples Which has a higher IE

Se or Cl? B or Sr?

Periodic Trends Ionization Energy Cont’d

There is also a 2nd and 3rd IE - always higher than the first. IE of elements greatly increases when the outer shell has been emptied.

Example Which has a higher 2nd IE, Na or Mg? Which has a higher

3rd IE - Al or Mg?Mg Na

Periodic Trends 4. Electron Affinity - energy absorbed when an electron is

acquired by a neutral atom. Basic idea - some atoms want to take on electrons - they

have a high electron affinity value - they receive a lot of energy when accepting electrons

Trend:

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Periodic Trend Electron Affinity Cont’d

Examples F or Na?

F = -322 kJ/mole Na = -53 kJ/mole F has a higher electron affinity - higher, more negative

value

Periodic Trends 5. Valence electrons - outer shell electrons involved with

bonding –tells you about an element’s chemical behavior

+

Sodium Chlorine Salt

Periodic Trends 6. Ionic Radius - the size of an ion.

Ions are created by gaining or losing electrons. Cation - positive, lost electrons

Metals tend to become cations Anion - negative, gained electrons

Nonmetals tend to become anions Cations are smaller than the neutral atom - why?

they lost a shell Anions are larger - why?

more electron repulsion so shells are pushed farther apart

Periodic Trends Ionic Radius Cont’d

Trend

Example Li+1 or Be+2 - Li is bigger because less protons pull the

shell in less O -2 or N -3 - N is bigger because less protons pull

the shell in less

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Periodic Trends 7. Activity (Reactivity)

metals - larger atoms are more active - why? they lose electrons more easily

nonmetals - smaller more active - why? they gain electrons more easily

Periodic Table

Reactivity Trends

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Metals Nonmetals

Most active metals + most active nonmetals = most stable compoundsex: RbF - very stable LiBr - less stable

Periodic Trends 8. Metallic character - some metals are said to be more

metallic than others - really it is just a statement about their activity. If they are more active, they are said to be more metallic. Trend

Which is more metallic? Ca or Na?

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