1 / 18

Bellwork : Friday, September 21st

Bellwork : Friday, September 21st. How are the elements on the periodic table organized?. Elements & Compounds. Chapter 3.4. Periodic Table: History. Dmitri Mendeleev first began to organize the elements by similarities in mass.

art
Download Presentation

Bellwork : Friday, September 21st

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bellwork: Friday, September 21st • How are the elements on the periodic table organized?

  2. Elements & Compounds Chapter 3.4

  3. Periodic Table: History • Dmitri Mendeleev first began to organize the elements by similarities in mass. • He was the first one to create a periodic table, though we no longer organize it by atomic mass

  4. Periodic Table Today • Arrange by atomic number (number of protons) • Organizes elements into a grid of horizontal rows called periods and vertical columns called groups or families • Elements in the same group have similar chemical and physical properties

  5. Elements- pure substances that cannot be separated into simpler substances by physical or chemical means • 92 naturally occurring • Others have been developed by scientists (synthetic) • Not equally abundant • Examples: 75% of universe is hydrogen and oxygen, carbon, and hydrogen make up 90% of the human body and francium is the least abundant element with only 20g total in the Earth’s crust • Each has a unique chemical name and symbol

  6. Element Symbols • Symbols are 1, 2, or 3 letters • First letter is ALWAYS capitalized • Remaining letters are ALWAYS lowercase • Universally accepted system so that scientists can communicate

  7. What elements do YOU need to know? • 4-5 quizzes • 3 announced • 1-2 unannounced • Quiz Monday, 24th (Actinium –Hydrogen) • Quiz Wednesday, 26th (Iodine-potassium) • Quiz Friday, 28th(Radium-Zirconium)

  8. Compounds • Made up of 2 or more different elements that are chemically combined • Most matter exists in this form • 10 million known compounds • New ones are created at a rate of 100,000/year • Can be broken down into simpler substances by chemical means • More stable than individual elements

  9. Identifying the number of atoms in a compound: • Coefficient: A number that comes in front of a chemical formula, indicates how many molecules of that compound you have. • Examples: 4CO23H2O • Subscripts: a number that is below the elements listed in the compound, indicates how many of each element you have. • These numbers only apply to the number in FRONT of them. • Examples: 4CO23H2O

  10. Let’s Practice! • Figure out how many atoms are in each compound!

  11. Bellwork: Monday, September 24th • Determine how many atoms are present in the following compounds: • 1. H3PO4 • 2. NH4H2PO4 • 3. 3CaCrO4 • 4. 4K2Cr2O7

  12. Law of Definite Proportions • A compound is always composed of the same elements in the same proportion by mass • The same amounts of the elements in a compound can be expressed by percent mass x 100

  13. Example Problem: • A 200.0g sample of sugarcane contains 32.5g of hydrogen. What is the percent by mass of hydrogen in the compound?

  14. Law of Multiple Proportions • The same elements can form more than one compound • Happens if different compounds have different mass compositions • Example: Water and Hydrogen Peroxide Mass ratio of compound I Mass ratio of compound II *Look at the example on page 89*

  15. Homework • Chapter 3 pg 977: 1-4 • Practice Problems: 19-22 pg 88 • Practice Problems: 28-29 pg 90

More Related