For today s lesson you will need:

Transcription

1 Periodic Table 8.5C interpret the arrangement of the periodic table, including groups and periods, to explain how properties are used to classify elements

2 For today s lesson you will need:

3 Before we really begin what are elements (again)? Substances that cannot be separated into simpler substances by chemical means So how do we know if this is an element? What about this substance? Elements are identified as 1 substance represented by 1-2 letters and can be found on the Periodic Table. We will add to this understanding as we learn in this unit.

4 This leads us to: How are elements arranged on the PT? A Little Periodic Table History

5 History of the Periodic Table Dmitri Mendeleev, a Russian scientist born in Siberia in 1834, is known as the father of the periodic table of the elements The periodic table is designed to help you predict chemical and physical properties of elements Key points are underlined, you might want to write them down!

6 Get out your Periodic Table and (colored) pencils

7 How to Read the Periodic Table: Step 1 View the periodic table as starting at the top left and ending at the end of the last row, near the bottom right. The table is structured from left to right in order of increasing atomic number. The atomic number is the number of protons in a single atom. Not every row or column is complete. Although there may be breaks in the center, reading the table will continue from left to right. For instance, Hydrogen has an atomic number of 1 and it is in the top left. Helium has an atomic number of 2 and it is in the top right. Elements 57/58 through 103 are usually pictured as a subset at the bottom right of the table. These are the rare earth elements.

8 Add these blue arrow to your table and label it atomic number Atomic number Atomic number The direction of the arrows show the pattern of increasing atomic numbers.

9 How to Read the Periodic Table: Step 2 Find a group of elements in each column of the table. There are 18 columns. Sometimes groups are referred to as families. A column of elements is called a group. Groups describe elements that share common properties, usually based on the number of valence electrons Numbering will usually be above the columns; however, it may appear below some groups, such as the metals. Add these arrows to your PT now. Label it as groups

10 A look at the second column, or group: If you looked at one atom of every element in this group you would see Each atom has the same number of electrons in it s outermost shell. How do I know that?? Think back to the Bohr Model

11 The group 2 elemental atoms all have 2 electrons in their outer shells: Be (Beryllium) Atom Mg (Magnesium) Atom

12 Valence Electrons Effect the way an atom bonds, which determines many of the chemical properties of the element, including reactivity Remember, atoms can have anywhere between 1 and 8 valence electrons This is why elements within a group usually have similar chemical properties because valence electrons govern how an element will react with other substances

13 Check point! Potassium has properties most similar to which of these elements? Lithium (Li) Beryllium (Be) Calcium (Ca)

14 How to Read the Periodic Table: Step 3 Find a period of elements in each row of the table. There are 7 periods. The periods are usually numbered 1 through 7 on the left hand side of the table. All of the elements in the same period have the same number of atomic shells (the area that the electrons live in) Each period is bigger than the last. This is associated with increasing energy levels of atoms on the periodic table.

15 How to Read the Periodic Table: Step 4 Understand additional grouping according to metal, semi-metal and non-metal. All of the groups are shaded differently so you can tell them apart. Elements are located in three main categories on the periodic table based on their physical properties Metals Nonmetals Metalloids Shade or circle these now on your PT

16 Physical Properties Physical properties can be observed or measured without changing the composition of matter. Physical properties are used to observe and describe matter.

17 Examples of Physical Properties Mass How much matter is in an object Color/Texture Malleable Can be pounded/rolled into a shape Ductile Can be stretched into a long wire Density How tightly mass is packed into an object

18 Metals

19 Metal Trends shown on the PT: 1. In METALS reactivity DECREASES as you go ACROSS a Period because though they still want to give away valence electrons they have more of them to get rid of, which requires more energy. 2. DOWN a Group: In METALS reactivity INCREASES as you go DOWN a Group because the farther down a Group of metals you go, the easier it is for electrons to be given or taken away, resulting in higher reactivity.

20 Metals Most elements are metals. The 88 elements to the left of the stairstep (or zig-zag) line are metals or metal-like elements. Physical Properties of Metals: Luster (shininess) Good conductors of heat and electricity High density (heavy for their size) High melting point Ductile Malleable

21 Nonmetals

22 Non-metals Nonmetals are found to the right of the stair-step line. Their characteristics are opposite those of metals. Physical Properties of Nonmetals: No luster (dull appearance) Poor conductor of heat and electricity Brittle (breaks easily) Not ductile Not malleable Low density Low melting point

23 Metalloids

24 Metalloids Elements on both sides of the zigzag line have properties of both metals and nonmetals. These elements are called metalloids. Physical Properties of Metalloids: Solids Can be shiny or dull Ductile Malleable Conduct heat and electricity better than nonmetals but not as well as metals

25 Chemical Properties A chemical property is a characteristic that is observed when a substance changes into a different substance.

26 Examples of Chemical Properties Combustible capable of igniting at higher temps Corrosion destruction of metals Reactivity undergoes a chemical reaction Oxidation rusting or tarnishing Flammable capable of igniting

27 Back to the PT: Each group has distinct properties The periodic Table is divided into several groups based on the properties of different atoms and how they react when combined with other elements For example

28 A closer look at the groups:

29 Alkali Metals Soft, silvery colored metals Very reactive!!! Reactions with water! h?v=uixxjtjpvxk

30 Transition Metals Most are good Conductors of electricity Malleable (easily bent/hammered into wires or sheets)

31 Nonmetals Brittle Do not conduct electricity

32 Most are Poisonous on their own, but when combine with another element Salt Forming Fairly reactive Halogens Na---Cl is table salt!!

33 Noble Gases Unreactive (inert) (State of Matter) Gases at room temperature Exist in Earth s atmosphere

34 Make your own Periodic Table! We will recreate just how Mendeleev must have felt when he was trying to organize his elements at the time.

35 Introduction: Video (click on pic):