Reactivity of Atoms Based on Their Placement in The Periodic Table

*Click the link below and check out the losers, takers, and kings analogy of the periodic table of elements! http://www.mansfieldct.org/schools/mms/staff/hand/chemkingoctet06.htm

And the "Elements Song" http://www.privatehand.com/flash/elements.html

1 The Periodic Law

Mendeleev developed his periodic table before the discovery of protons. He did not know that two elements could not have the same number of protons.

Key Concept: In the modern periodic table, elements are arranged by increasing atomic number (number of protons)

2 Periods

Each row in the table of elements is a period

3 The number of elements per period varies because the number of orbitals increases from energy level to energy level

4 Groups

Each column on the periodic table is called a group (sometimes called a family)

5 Key Concept: Properties of elements repeat in a predictable way when atomic numbers are used to arrange elements into groups.

The elements in a group have similar electron configurations. An element's electron configuration determines it's chemical properties

6 What do you call a joke that is based on cobalt, radon, and yttrium?

CoRnY !!!!!

7 Atomic Mass Unit

Because the mass of an atom is extremely small, scientists created the atomic mass unit.

How? Scientists assigned 12 atomic mass units to carbon­ 12 which has 6 protons and 6 neutrons.

An atomic mass unit (amu) is defined as one twelfth the mass of carbon­ 12 atom

8 Atomic Mass

The atomic mass of chlorine is 35.453. How was this calculated?

There are two natural isotopes of chlorine, chlorine­35 (17p+ and 18n) and chlorine­ 37 (17p+ and 20n)

35.453 is a weighted average because the percentage of Cl­35 that is found in nature is 75.78% and percentage of Cl­37 is 24.22%

So.... if you multiply those occurrences with their masses, add them together, and divide by 2 to get the mass of 35.453)

9 Classes of Elements

Elements can be classified as solids, liquids, or gasses based on their states at room temperature.

• Solids • Liquids • gases

10 Classes of Elements

Elements are also classified based on whether the occur naturally or not

Elements that do not occur naturally have an atomic number greater than 92

Check them out....

11 Metals

The majority of elements are classified as metal:

Metals are: • good conductors of electric current and heat • solid at room temperature (except Mercury) • most are malleable

12 Transitional Metals

Metals in groups 3­12 are called the transition metals

13 Nonmetals

Poor conductors of heat and electricity

Many are gasses at room temperature

Some are very reactive, some are not

Example: Fluorine is the most reactive nonmental

14 Metalloids

Properties fall between metals and nonmetals

Example: Metalloid's ability to conduct electric current varies with temperature

Example: Silicon (Si) is a poor conductor at room temperature but a good conductor at high temperatures

15 Variation Across a Period Key Concept: Across a period from left to right, the elements become less metallic and more nonmetallic in their properties

The most reactive metals are on the left of the periodic table and the most reactive nonmetals are on the right in group 17

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