Agenda Reading for the night: Ebola Vocabulary Check Lesson: Mendeleev History One Element at a time project

Organizing the Elements

Looking for Patterns in the Elements Record the activities of a typical day: Monday:Tuesday:Wednesday:Thursday:Friday:

Notice any patterns Matter is made up of about 100 different elements that have a variety of properties These elements like your daily activities follow a pattern.

Mendeleev, the Detective 1800’s scientists suspect the elements could be organized in useful way. be organized in useful way. 1869, Russian scientist, Dmitri Mendeleev, Dmitri Mendeleev, recognized a hidden pattern in the elements. pattern in the elements.

One of his first observations was that some elements have similar chemical and physical properties. Examples: Fluorine and Chlorine, both gases that irritate your lungs if you breathe them in. Silver and Copper are both shiny metals that gradually tarnish if exposed to air.

Mendeleev believed that these similarities were important clues to the pattern he was looking for. He wrote the facts about the elements on paper cards. He wrote all the properties he knew about an element, including its melting point, density and color.

Mendeleev also recorded two other important properties: atomic mass bonding power. The atomic mass is the average mass of one atom of an element.

~ Mendeleev found the atomic mass of elements from the elements comparison to hydrogen, the lightest of elements. ~ Bonding power refers to the number of chemical bonds an element can form. ~ This was determined by studying how each element formed compounds with oxygen.

First Periodic Table ~ Mendeleev took his note cards and began to arrange them in different patterns. ~ He noticed that patterns appeared when the elements were arranged in order of increasing atomic mass. He noticed that the elements bonding power changed in an orderly way too ~ He noticed that patterns appeared when the elements were arranged in order of increasing atomic mass. He noticed that the elements bonding power changed in an orderly way too.

~ As Mendeleev discovered, arranging the elements by increasing atomic mass does not produce a perfect table. ~ He moved the cards to positions where they fit be. ~ By doing so this left 3 blank spaces. He boldly stated that these spaces would be filled in eventually because they had not yet been discovered.

~ 1869 Mendeleev published the first periodic table of elements. ~ Periodic means “regular repeating pattern”. ~ In the modern Periodic Table, the properties of the elements repeat in each row – or period – of the table. ~ Within the next 16 years scientists found Mendeleev’s missing elements.

Homework 1. Begin your project: pick an element 2. Research that element: fill in the graphic organizer 3. Finish nightly reading and questions