Mrs. NielsenChemistry

The History of the Periodic TableBy 1860, more than 60 elements had been discovered, but scientists had no way of organizing the elements.

Dmitri Mendeleev’s first published periodic table

A spiral periodic table

Developed by Henry Moseley in 1911 Elements are organized by increasing atomic number Elements with similar properties occur at regular intervals

Rows = “periods” Properties vary across a period

Columns = “groups” or “families” Similar bonding capabilities Elements in a compound may be replaced by other

elements in the same family.

Families of Elements

Group 2: Alkaline Earth metals

Highly reactive

Group 3-12: Transition metals

Group 17: HalogensVery reactive, often react with

alkali metals

Group 18: Noble GasesUnreactive, already “happy”

Group 1: Alkali MetalsHighly reactive, not found as free

elements in nature

Why are Br and Hg a different color?

Metals (“downstairs”) good conductors of heat and electricity malleable ductile tensile strength luster

Non-Metals (“upstairs”)

poor conductors of heat and electricity

Metalloids (on the stairs)

semi-conductors of heat and electricity

Use the white boards with periodic tables to complete the following tasks.

Put a star around the alkali metal that has 3 protons.

Shade in the noble gas that is in the 4th period.

Circle the halogen that is a liquid at room temperature.

Put a square around the transition metals.

Label the Lanthanide series with an L.

Label the Actinide series with an A.

Draw a triangle around 2 of the metalloids.

Put an “X ” through the non–metal in Group 14.

Draw a over the alkaline earth metal with an atomic #

of 20.

The Periodic Table as a

REFERENCE TOOL

29

Cu

63.55 Average Mass= a weighted average based on how common an isotope

is.

Element Symbol

Atomic # = # of protons

How do I use the periodic table as a reference tool?

Examples: 1) You have 100 marbles.

25 marbles have a mass = 2.0g75 marbles have a mass = 3.0g

2) There are 2 forms of naturally occurring copper.

Copper – 63 (69.17%) = 62.929598 amuCopper – 65 (30.83%) = 64.927793 amu

.6917 (62.929598) + .3083 (64.927793) = 63.55 amu

.25 (2.0g) + .75 (3.0g) = 2.75 g

The mass of an element can be used to determine either the atomic mass or the molar mass.

Atomic Mass Molar Mass

Units: Atomic mass unit (amu)

= the mass of 1 atom of any element.

One helium atom has a mass of 4.002 amu

Units: grams per mole (g/mol)= the mass of 1 mole of

atoms of any element.

One mole of sulfur atoms has a mass of 32.066 g/mol

What do these new units mean?

Atomic Mass Units (amu) 1 amu = 1.660504 x 10-

24 g Carbon – 12 is set as the

standard measurement at 12 amu.

Therefore, the atomic mass of any element is found by comparing its mass with Carbon-12.

Grams per Mole (g/mol) How many items are in

1 mole?

Yes indeed! There are 6.02 x 1023 items in 1 mole.

The current world population is approximately 7 billion people.

If everybody in the world was working together to count one mole of atoms, and each person is counting at a rate of 1 atom/second, it would take over 2.7 MILLION YEARS to count all of the atoms in one mole!

Conclusion: 6.02 x 1023 is a REALLY BIG number!