Elements and The Periodic Table

Elements: Chemistry is the study of matter and its changes. Elements make up an incredible variety of different substances. An element is a pure substance that cannot be broken down or separated into simpler substances. Each element is one kind of atom. By studying elements, we can learn more about the structure of matter

Element names and symbols: Because elements have different names in different languages, chemists use international symbols for them. Each element is given a symbol – makes them easy to recognize (universal across languages), and less cumbersome than writing the entire name every time. Chemical symbols consist of one or two letters. Ancient names are used as the source of many of the symbols. Example: Mercury - Hg - Hydragyrum (Latin for liquid silver)

Element names and symbols Continued: These symbols are used when writing compounds, and show the proportions of each chemical present. Water is H2O, we have two Hydrogen Atoms and one Oxygen atom to make Water. Carbon Dioxide Gas is CO2, we need one atom of Carbon and two atoms of Oxygen to create Carbon Dioxide Gas. Rules for creating the symbols: 1st letter of the name, or 1st plus another letter if the 1st one was already taken. Ex C --> Carbon, Since C is used for Carbon all other elements that start with C must have a second letter. Cu  Copper, Co  Cobalt. Sometimes this rule is over-lookd, Zn  Zinc, even though there are no elements with just ‘Z’ Elements that were found first get their symbols from their Latin names. 1st letter is always capitalized, 2nd letter is always lower case.

Classifying Elements All elements are different from each other. The properties – both physical and chemical – are unique to each element and therefore can be used to identify what element you have. Some elements do have SIMILAR chemical and physical properties however, making it a bit tricky to identify exactly which element you have. To make our understanding of chemistry easier, we group the elements according to their properties.

Organize the Items Each group is given a package of items (a deck of cards, food items, and geometric shape with different colours and size) Your job is to organize these items in a logical and methodical manner. Note there are items that are missing from each set. Discuss with the class why you arranged the items the way you did.

Elements can be organized by their properties. 1860s: Dmitri Mendeleev Russian teacher and chemist Looked at different ways to organize the elements Wrote properties of elements on cards so that he could rearrange them and compare properties (“chemical solitaire”) Properties included atomic mass (average mass of an atom of an element), density, and melting point Figure 2.7: A) Dmitri Mendeleev B) Mendeleev wrote the properties of elements on cards like this one so he could rearrange them and compare properties.

The Predictive Power of Mendeleev’s Table Mendeleev’s periodic table: Ordered the elements by increasing atomic mass Grouped elements into “families” based on similar properties (density, melting point) Left gaps in his periodic table to predict the existence of elements not yet found yet These missing elements would have properties similar to other elements in the same families Example: He noticed that Hydrogen had a weight of 1 g, Lithium had a weight of 7 g, Sodium had a weight of 23 g and Potassium had a weight of 39 g. He then noticed Beryllium had a weight of 9 g, Magnesium had a weight of 24 g, and Calcium had a weight of 40 g.

The Predictive Power of Mendeleev’s Table (continued) Figure 2.8: The gaps in Mendeleev’s table predicted the existence of yet-to-be-discovered elements. Mendeleev used the properties of other elements in the same families to predict the properties of these elements.

The Genius of Mendeleev’s Periodic Table https://www.youtube.com/watch?v=fPnwBITSmgU

Assignment Assignment Pg 192 Questions 1, 3 - 7, 16, 17; Pg 196 Questions 3, 4, 5, 7 (d), 8, 10, 11, 12.