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The Periodic Table. Chapter 17 Section 3. Periodic. The word periodic means “repeated pattern”. Lunar Cycle Days of the week Months of the year Seasons. Dmitri Mendeleev. A Russian chemist in the late 1800’s who looked for a way to organize the elements using a “ periodic pattern”.

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  • The word periodic means “repeated pattern”.
  • Lunar Cycle
  • Days of the week
  • Months of the year
  • Seasons
dmitri mendeleev
Dmitri Mendeleev
  • A Russian chemist in the late 1800’s who looked for a way to organize the elements using a “periodic pattern”.

Mendeleev organized his chart from lightest-to-heaviest elements and then used a repeating pattern based on the Physical & Chemical properties of the elements.

leave the empties
Leave the empties!
  • Mendeleev had to leave some places in his chart blank because there where no known elements that fit into that spot.
  • Mendeleev predicted that there might be more elements that had not yet been discovered that could fit into those spots.
  • Once these predictions were made, other scientists started looking, and guess what?
found it
Found it!

The prefix Eka mean close to or related to.

Germanium was discovered by a ________ scientist.

Gallium was discovered by a ________ scientist.

there s always room for improvement
There’s Always Room for Improvement
  • Every time a new element was discovered the periodic table would be updated.

This is what is looks like today.

Every empty green slot is a spot where Mendeleev predicted an unknown element would go.

Mendeleev’s Predicted Elements

Every white slot represented a possible unknown elements, but Mendeleev did not have enough information to make predictions about the properties of these elements.

organizing the periodic table
Organizing the periodic table
  • Mendeleev organized elements by mass and chemical properties.
  • The Vertical columns are called groups, or families.
    • These are elements that have similar chemical properties.
    • The chemical properties of an atom are based on the number of electrons orbiting around the nucleus.
organizing the periodic table1
Organizing the periodic table
  • The first family or group called the alkali metals contains:
    • Li, Na, K, Rb, Cs, Fr
  • These are dull grey, soft, metallic compounds that react violently with water.

Disposal of Sodium

Brainiac – Alkali Metals

electron cloud structure
Electron cloud structure
  • Not all electrons orbit at the same distance from the nucleus.
  • Each separate orbit is called an energy level or shell.
  • The 1st orbital shell can only hold a maximum of 2 electrons.

Hydrogen & Helium

more orbital shells
More orbital shells


  • Once the 1st shell is filled, we move on to a new orbital shell.
  • The second shell can hold a maximum of 8 electrons.


electron energy levels
Electron energy levels
  • Level 1 – 2 electrons
  • Level 2 – 8 electrons
  • Level 3 – 18 electrons
  • Level 4 – 32 electrons
  • Level 5 – 50 electrons
let s make this easier
Let’s make this easier!
  • With the exception of the first energy level, all other elements repeat their chemical properties in a patter of 8’s
    • We call this an Octave.
  • Every atom wants to be stable.
    • This means getting as close to 8 electrons as possible in the outer shell.
    • These electrons in the outer shell are called Valence electrons.
    • Valence electrons are responsible for all chemical reactions between atoms.
here s the easy part
Here’s the easy part
  • Instead of drawing pictures of the entire atom, we will ONLY draw the valence electrons.
  • We will use the chemical symbol for the atom and dots to represent the electrons.
4 rooms 2 to a room
4 rooms, 2 to a room.
  • Each group is labeled by the number of valence electrons in the outer electron shell.
this is the lewis dot structure
This is the Lewis dot structure!
  • We will use the Lewis dot structure

(a.k.a. – electron dot diagram) to help us figure out how elements interact with each other to do chemistry!

  • Let’s get in some practice!