The Periodic Table

Chapter 18 Section 3

Organizing Elements

• Demo - • How did we organize the water?• What was the basis of our

organization?

Organizing Elements

• Dmitri Mendeleev organized elements based on increasing atomic masses.

• The periodic table still contains elements in order, but now by increasing atomic number and by changes in physical and chemical properties.

Mendeleev

• He actually created the periodic table and left blank spaces to keep the organizational flow going…

• Based on this information, Mendeleev could predict the properties and the mass numbers of new undiscovered elements.

• How was Mendeleev’s predictions?

Mendeleev

• Unlike Vodoo Claire…

• His predictions were extremely accurate!

Improving the Periodic Table

• Mendeelev was successful…but like any first attempt, it needed some work.

• The periodic table was modified and now arranged by increasing atomic numbers instead of atomic mass.

The Atom and The Periodic Table

• Just sorting and organizing your sock drawer, so is the periodic table.

• There are two ways the periodic table is organized– Groups/Families– Periods

Groups/Families

• Groups or families are the vertical columns on the periodic table.

• Groups are numbered 1 through 18.

• These elements have the same number of electrons in their outer orbits.

• They also have many characteristics in common.

The group IIa elements; beryllium, magnesium, calcium, strontium, & barium. They are called the Alkali Earth Metals.

Electron Cloud Structure

• Review - where are the protons, neutrons, and electrons located?

• Where are the electrons located?

• How many electrons are there?

Electron Cloud Structure

• Electrons within the Electron Cloud Structure have different amounts of energy.

• The energy levels closer to the nucleus have less energy

• Electrons fill the inner most energy first.

Electron Cloud Structure

• Elements in the same group, have the same number of electrons in their outer most shell.

• This is the number that determines each element’s chemical properties.

• How many dots should Cl have? • How many dots should F have? • How many dots should Br have?

Energy Levels

• The energy levels are named using numbers one through seven.

• Energy level 1 can have a maximum of two electrons.

• Energy level 2 can have a maximum of eight electrons.

• Energy level 3 can have a maximum of 18 electrons.

Energy Levels

• When the energy levels have the maximum number in their shell, they are considered complete and stable.

• Remember, the electrons fill the innermost energy levels first.

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Rows on the Table• Remember, the atomic number = the

number of electrons.• The first row has Hydrogen with one

electron and Helium with two electrons both in energy level one.

• Therefore, Helium has the first energy level full of complete and is considered stable.

Rows on the Table• If you look at the second row, it starts with

lithium and ends with neon.• Lithium has three electrons and neon has

ten electrons. • Lithium has two electrons in the first shell

and one in the second. • Neon has two electrons in the first shell and

eight in the second.• The first column always starts the new

shell.• The last column always fills the shell.

Electron Dot Diagram

• Elements in the same group have the same number of electrons in their outer energy level.

• Electron Dot Diagram uses the symbol of the element and dots to represent the electrons in the outer energy level.

Same Group - Similar Properties

• The elements in group 17, halogens, have similar EDD.

• All halogens have seven electrons in their outer energy level.

• Because they have the same number of electrons in their outer energy level, they will all undergo chemical reactions similarily.

Same Group - Similar Properties

• A common property of halogens is the ability to form compounds easily with group 1.

• Group 1 elements have only one electgron in their outer energy level.

• Group 17 has seven.• The two groups come together and

share their electrons - ie - sodium and chlorine = NaCl.

Same Group - Similar Properties

• Not all elements combine easily with other elements.

• The elements in group 18 have complete outer shell and don’t need any other elements to be stable.

Regions on the periodic table

• The horizontal rows of elements are called periods.

• The elements increase by one proton and one electron as you go from left to right.