The Periodic Table

1. So you thought you knew ... The Periodic Table

2. Mendeleev’s Arrangement • By mid-1800’s, chemists needed a way to organize the 50+ elements already discovered • Russian chemist, Dimitri Mendeleev found a pattern when he placed the elements in order of increasing atomic mass • The properties of the elements appeared in regular intervals, or periodically - hence, the PeriodicTable

3. The Modern Periodic Table • Most elements with atomic numbers less than 93 are natural - the exist naturally on Earth • The other elements are synthetic (man-made) • Once the relationships between elements were established, scientists could predict other elements that could be made • Based on what the atomic structure should be (according to position on periodic table)

4. Classes of Elements • We can predict the physical and chemical properties of an element based on its position in the table • 3 classes: • Metal • Non-metal • Metalloid • Copy the following table into your notes:

5. Classes of Elements cont’d

6. Classes of Elements cont’d

7. Where are they on the PT? Non-Metals Metals Metalloids

8. In-Class Assignment: • Read pages 202 – 204: Mining For Metals; Metals and Health; Diamond Mining. Answer the following questions: • What compound is used to extract gold from ore? • What are the negative effects of gold mining and refining? • How is iron used in your body? • What organs can be injured if iron levels in the body are too high? • Name the two processes that result in high concentrations of metals in animals. • Why are waterways a key source of mercury poisoning? • Answer question 1 on p. 203. • In point form, describe four ways diamond mine companies contribute to their local communities. Do you think mine companies did this around 100 years ago?

9. What Else Can the Periodic Table Tell Us? • Elements are organized into periods and groups • Periods are horizontal rows, • numbered 1 to 7, starting from the top

10. Rows and rows... • Even though they skip some squares in between, all of the rows go from left to right • Elements in the same row have something in common - the same number of energy levels (or electron shells) • Every element in the top row (the first period) has one electron shell for its electrons • All of the elements in the second row (the second period) have two electron shells for their electrons, etc • At this time, the maximum number of energy levels or electron shells for any element is seven

11. Groups • Groups (or families) are vertical columns • They are numbered 1-18, starting on the left

12. Groups • When a column goes from top to bottom, it's called a group. • The elements in a group have the same number of electrons in their outer energy shell • Every element in the first column (group one) has one electron in its outer shell. • Every element on the second column (group two) has two electrons in the outer shell... etc • N.B. There are exceptions to the order when you look at the transition elements, but you get the idea. • For now, “1,2, skip a few, minus 10”

13. Happy Atoms • Electrons want to be happy • They are happiest when their outermost energy level is full of electrons! • During a chemical reaction, one atom can join with another atom by gaining, losing, or sharing valence electrons • Valence electrons determine how reactive an element is

14. All in the Family (Anybody? Anybody?) • Families are groups of elements with similar chemical properties • Each family reacts and behaves differently • 4 important families are • Alkali Metals • Alkaline Earth Metals • Halogen Gases • Noble Gases

15. Alkali Metals (Group 1) • Traits: • Very reactive – why? • They all have 1 electron in their outer shell. That’s 1 away from being happy (full shell) • Increased desire to bond (and lose electron) = more reactive

16. Alkali Metals cont’d MORE TRAITS: Eg. sODIUM • Low melting points • Shiny • Light in weight • Soft

17. Alkaline Earth Metals – Group 2 • 2nd most reactive family • Needs to get rid of 2 valence electrons to be happy • When heated, they will burn in air and produce bright, colourful flames • Eg. Magnesium • Often used in fireworks • Very important in physiology • Eg. calcium • Eg. Magnesium

18. Halogens – Group 17 • How many valence electrons ? • 7 – only 1 short of being full • Because they are so close to being happy, they combine with many different elements • Very reactive non-metals! • Often bond with elements from Group 1

19. Halides • Extremely corrosive • Chlorine and Iodine are both used as disinfectants • When a halogen combines with another element, the compound is called a halide • Sodium Chloride (NaCl) is a halide

20. Inert Gases - Group 18 • Aka Noble gases • Aka group zero • Happiest elements of all! • Outer electron shells are full • Happy not reacting with other elements – rarely combine • Non-reactivity = inert • Odourless, colourless gases (at room temp.) • When they do bond, they were forced

21. Outlaws: Hydrogen helium Even though it only has 2 valence electrons, it is still in the inert gas family There’s one in every family, right? • Has talents of 2 groups: one and seven • either missing an electron or have one extra • NOT an alkali metal • It’s a gas

22. Transition Metal Groups • Transition metals (groups 3-12) are special • They have a lot of electrons that are distributed in different ways (i.e. They don’t follow the pattern) • Can use the two outermost shells to bond with other elements (instead of just outermost) • Most have two shells that aren’t “happy”

23. The last two... Lanthanide series Actinide series All radioactive elements Some with higher atomic numbers have only been made in labs Particle accelerators • Aka: Rare-earth metals or inner transition metals • Found naturally on earth • Except for Promethium (Pm) - radioactive