Periodic Table NotesTopic Two

Dmitri Mendeleev is credited as the first scientist to start organizing the known elements. He began this process by looking at the physical properties, chemical properties and the element’s atomic mass.

He started noticing that patterns could be found within his table; certain types of elements behaved in similar manners.

At this point only a small number of the elements had been discovered. Mendeleev left spaces in his Periodic table for the missing elements.

When more of the elements were discovered, it was determined that the elements could not be correctly organized by atomic mass.

Another scientist, Moseley, assigned atomic numbers to the known elements which would later be used to determine the number of protons in each atom’s nucleus.

This method is currently used to arrange the elements that make up the Periodic Table.

The Setup•The Periodic Table is arranged using Periodic Law.

•This highlights the similar physical and chemical properties that are found within the different elements.

Types•There are 3 types of elements.▫Metals▫Nonmetals▫Metalloids

Periods•There are 7 periods found in the Periodic Table.

•Periods are the horizontal rows.

•The radii of the atoms decreases as your travel from left to right across the table.

Groups•There are 18 groups, or families, found in the Periodic Table.

•Groups are the vertical columns.

•The radii of atoms increases as your travel from top to bottom.

x

x

x x

x x

x

PeriodsG

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1

2

3 4 5 6 7 8 9 10 11 12

13 14 15 16 17

18

1

2

3

4

5

6

7

NONMETALS

METALS

METALLOIDS

Metals•Metals make up over two-thirds of the elements in the table and are found on the left side.

Properties of Metals•Shiny•Ductile (drawn into wire)

•Malleable (bendable)•Good conductors of heat and electricity

Nonmetals•Nonmetals are found on the right side of the table.

•Group 18 contains the Noble gases, these elements do NOT like to react with other elements.

Properties of Nonmetals•Dull•Brittle•Poor conductors of heat and electricity

Metalloids•Metalloids are found in between the metals and nonmetals.

•There are only 7 of them.

Properties of Metalloids•Have properties of both metals and nonmetals

•They are…•B, Si, Ge, As, Sb, Te, At

Group 1•The alkali metals are found on the left side of the table.

Properties•They are all soft, silvery-white metals with low melting points.

•They are so reactive that they will burn the skin if touched and are never found in nature in their pure forms.

Elements•Lithium•Sodium•Potassium•Rubidium•Cesium•Francium

Group 2•The alkaline earth metals are found on the left side of the table.

Properties•All members of this group are soft and silvery-white, but have high melting points and densities.

•They are good conductors of electricity and are never found in nature in their pure forms.

Elements•Beryllium•Magnesium•Calcium•Strontium•Barium•Radium

Group 3-12•The transition metals are found in the middle of the table.

Properties•It is the largest family with 40 members.

•Elements in this family produce colored solutions.

•Most are solids at standard temperature except mercury which is a liquid.

Lanthanide & Actinide Series

•These are found underneath the rest of the table..

Lanthanide Series•These elements are commonly referred to as the rare-earth metals.

Actinide Series•These elements are all radioactive.

Group 13-16•The BCNO family is found on the right side of the table.

•It is a large family with 25 members and is the most diverse grouping.

Properties•The members of this group include all 3 types of elements.

•Most are solids but a couple are gases. (N and O)

Group 17•The halogens are found on the right side of the table.

Properties•All halogens are toxic.•This group contains all 3 phases of matter.

•F and Cl are gases•Br is a liquid•I and At are solids

Properties•Halogens combine with metals to form SALT compounds.

Group 18•The noble gases are found on the right side of the table.

Properties•These gases are colorless, odorless and tasteless.

•They are unreactive but will conduct an electric current.

•Each gas glows its own unique color.

Periodic Table TrendsPart Deux

Atomic Radius•size of an atom•measured from the center of the nucleus to the outermost point of it’s electron cloud

Radii across the Periods•As you go from left to right the number of protons and electrons increases and the number of energy levels stays the same.

Looks like this in Period 2…

•More protons… more electrons… same number of energy levels

What happens and why…

•The increase in the number of protons causes a decrease in the radius of the atom

•The positive charge on the protons is able to “hug” the negative electrons closer to the nucleus

Radii down the Groups•As you go from top to bottom the number of protons and electrons increases and the number of energy levels increases.

Looks like this in Group 2…

•More protons… more electrons… and more energy levels!

What happens and why…

•The increase in the number of energy levels causes an increase in the radius of the atom

Biggest vs Smallest•Helium has the smallest radius = 32 pm

•Francium has the largest radius = 270 pm

It’s not the size that matters… well actually, it is!

•Larger = more reactive

•Francium is the most reactive of the elements, Fluorine is the least reactive

Ionization Energy•energy needed to remove an electron from an atom’s electron cloud

I.E. across the Periods•The radius of an atom decreases as you go from left to right and the ionization energy increases as you go from left to right

What happens and why…

•The closer the electrons are to the nucleus, the tighter the proton “hug” is on the electrons.

•The tighter the “hug” is, the more energy is needed to remove an electron to create an ion.

I.E. down the Groups•As you go from top to bottom the radius of the atoms increases and ionization energy decreases.

What happens and why…

•The farther the electrons are from the nucleus, the looser the proton “hug” is on the electrons.

•The looser the “hug” is, the less energy is needed to remove an electron to create an ion.

Biggest vs Smallest•Helium has the greatest ionization energy = 2372 kJ/mol

•Francium has the smallest ionization energy = 393 kJ/mol

Electronegativity•Ability of an atom to attract electrons needed to fill its valence energy level

EN across the Periods•The radius of an atom decreases as you go from left to right and the electronegativity (EN) increases as you go from left to right

What happens and why…

•The greater the number of electrons in the valence energy level, the more stable the atom is. (less reactive)

•The closer you get to a full energy level the easier it is to attract electrons.

EN down the Groups•As you go from top to bottom the radius of the atoms increases and the electronegativity decreases.

What happens and why…

•The greater the number of energy levels the less stable the atom is. (more reactive)

•The larger the atom, the harder it is to attract electrons.

Biggest vs Smallest•Fluorine has the greatest electronegativity = 4.0

•Francium has the smallest ionization energy = 0.7

•The noble gases do NOT want to attract electrons because they are full!