Atomic Structure & the Periodic Table CHAPTERS 4 & 5

Transcription

1 Atomic Structure & the Periodic Table CHAPTERS 4 & 5

2 Objectives Understandings: Chemical structure determines the properties of matter The identity and properties of individual elements is determined by its Atomic number (protons). The relative locations on periodic table are connected with chemical reactivity Essential Question(s): What is the arrangement of subatomic particles in an atom and how does this affect the formation of compounds? How is the periodic table arranged and what patterns are present? How does particle size of a substance affect its properties? (macro, micro, vs. nano) How does the location of an element on the periodic table help determine its reactivity? Students Will Know: The currently accepted model of the atomic structure The difference between the atomic mass and the atomic number The size and scale of atomic particles The difference between a group and a period of the periodic table Students will be able to: Draw an atom with correct placement of electrons, protons, neutrons based on Modern Atomic Theory Differentiate between an ion, isotope, and neutral atoms Recognize the periodic table s organization by atomic number, electron level, and similar characteristics of elements Determine the atomic mass and atomic number for the common elements using the periodic table and be able to predict the placement of an unknown element.

3 Websites

4 Chapter 4: Atomic Structure What I need to know: Be able to compare and contrast the different theories of atomic structure Know the basic properties, size, function, and location of the 3 subatomic particle Neutron, Proton, Electron Use the periodic table and diagrams to determine the atomic number and the mass number of an element Understand the difference between a neutral atom, isotope, and ion Understand Modern Atomic Theory Energy levels Electron cloud model Atomic orbitals and electron configuration (p118)

5 The Atom Song

6 The History of Atomic Structure Greeks - Democritus Dalton Thomson Rutherford Bohr Modern Atomic Theory

7 The Models

8 Greeks Democritus the first to name the atom hypothesized that all matter is composed of tiny indestructible units, called atoms. atoms themselves remain unchanged, but move about in space to combine in various ways to form all objects

9

10 Thomson discovered the first component part of the atom: the electron, a particle with a negative electric charge. J.J. Thomson suggested the"plum pudding" model. In this model the electrons and protons are uniformly mixed throughout the atom:

11 Rutherford Discovers the Atoms Nucleus Stated that the atom as has a central positive nucleus surrounded by negative orbiting electrons. This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space.

12 Rutherford - Gold Foil Experiment This experiment involved the firing of radioactive particles through minutely thin metal foils (notably gold) and detecting them using screens coated with zinc sulfide (a scintillator). Rutherford found that although the vast majority of particles passed straight through the foil approximately 1 in 8000 were deflected leading him to his theory that most of the atom was made up of 'empty space'.

13 Neils Bohr This model was proposed by Niels Bohr in 1915; Often called the planetary model (but it is not that simple) it is not completely correct, but it has many features that are approximately correct.

14 Bohr This shows a Bohr model Electrons are in energy shells or levels 2 in the first 8 in the 2 nd 18 in the 3 rd Never, more than 8 in the outer most shell Outer most are called Valence electrons

15 Electron Cloud Model (1920's)- An atom consists of a dense nucleus composed of protons and neutrons surrounded by electrons that exist in different clouds at the various energy levels. The correct theory of the atom is called quantum mechanics; the Bohr Model is an approximation to quantum mechanics. The Electron Cloud model is a more realistic model

16 Atomic Structure Practice Worksheet Packet: Counting Atoms WS Drawing Atoms Atomic Dimensions Atomic Math Using the Periodic Table to get info on Atoms

17 Atomic Structure Proton Carries a positive charge and is found in the nucleus The atomic number and number of protons in an atom is always the same The atomic number identifies what the element is on the periodic table Example: Oxygen has an atomic number of 8 so it has 8 protons in its nucleus

18 Neutrons Found in the nucleus They are neutral and do not carry an electrical charge The number of neutrons can vary within the element, but when they do, the element becomes an isotope

19 Electrons Electrons carry a negative charge They are found outside the nucleus They are very small compared to the protons and neutrons They are found in energy levels moving around the nucleus but they may be in any area of the electron cloud Elements bond with other elements at the electron level

20 The Size of the Nucleus In the drawings above, the nucleus is too large. Or, put another way, if the nucleus is going to be that large, the electrons are too close. Real atoms are mostly empty space. If we wanted our drawings to be accurate, we would have to place the electrons about a mile away. Clearly, it would be difficult to bring a drawing that large to class.

21 Isotopes Isotopes Isotopes are atoms of the same element that have different numbers of neutrons in the nucleus. Remember that it is only the number of protons that determines the identity of an element. Let's look at the simplest element, hydrogen. The common variety of hydrogen has a single proton in the nucleus and a single electron in an orbital surrounding the nucleus.

22 Isotopes of Hydrogen The common variety of hydrogen has a single proton in the nucleus and a single electron in an orbital surrounding the nucleus.

23 Isotopes of Hydrogen Deuterium There is another variety of hydrogen that has a neutron in the nucleus as well as the proton. It still has only 1 proton so it remains the element hydrogen but now it weighs twice as much. This is an example of an isotope and this isotope of hydrogen is called deuterium. When it is combined with oxygen in the compound water; that water is called heavy water because indeed it is heavier than ordinary water. We call deuterium a stable isotope

24 Isotopes of Hydrogen Tritium There is still another isotope of hydrogen, called tritium, that has 1 proton and 2 neutrons in the nucleus.

25 Drawing Models of Isotopes 8 Carbon-12 Carbon-14

26 Naming Isotopes Carbon-12 Carbon-14 Uranium-238 Uranium Oxygen 14 Oxygen - 16 The number following the element name is its mass number. We identify different isotopes by their mass number since that is what makes them isotopes in the first place. They just have a different number of neutrons in the nucleus. The number of PROTONS Always remains the same.

27 Ions Ions are charged particles When an atom loses or gains an electron the atom becomes a charged particle Group 1A readily give away their valence electron, when they do they form positive ions EXAMPLE: Lithium gives away its electron it forms Li + (a positive 1 ion)

28 Drawing Bohr Models Wrap-up Purpose: Energy Levels To show all subatomic particles Protons Neutrons Electrons To show atomic # To show mass # To show idea of a neutral atom To show the idea of an ion

29 The Periodic Table Organization and Characteriestics

30 Periodic Table History Mendeleev gets credit for the arrangement of the modern periodic table See Section 5.1 p The modern periodic table is arranged by increasing atomic number (number of protons)

31 The Periodic Table

32 Classes of Elements Metals Solids at room temp. (except mercury) Good extremely reactive Groups 3b -12b are Transition Metals See chart: p. 132 Non-metals Poor conductors of heat and electric current Low boiling points, most gases at room temp Nonmetals that are solids at room temp. tend to be brittle Metalloids Their properties fall between metals and nonmetals Metalloids ability to conduct electric current varies with temp.

33 Metals Metals tend to lose electrons to form positive ions rather than to gain electrons and become negative ions

34 Metals - Continued Metals makeup more than 75% of the elements in the periodic table. Metals are characterized by the following physical properties. 1. They have metallic shine or luster. 2. They are usually solids at room temperature. 3. They are malleable. Malleable means that metals can be hammered, pounded, or pressed into different shapes without breaking. 4. They are ductile meaning that they can be drawn into thin sheets or wires without breaking. 5. They are good conductors of heat and electricity.

35 Metals vs. Non-metals

36 Non-Metals There are 17 nonmetals in the periodic table, and they are characterized by four major physical properties. 1. They rarely have metallic luster. 2. They are usually gases at room temperature. 3. Nonmetallic solids are neither malleable nor ductile. 4. They are poor conductors of heat and electricity NonMetals shown in BLUE

37 Metalloids Metalloids are in PURPLE

38 Periods All of the elements in a period have the same number of atomic orbitals There are 7 rows or periods Atomic number increases across rows

39 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 orbital. Members of groups have have similar electron configurations Electron configuration determines its chemical properties There are 32 columns or groups

40 Special Arrangements Hydrogen and helium are special elements. Hydrogen can have the talents and electrons of two groups, one and seven.

41 Families: Groups or Columns EXAMPLES OF FAMILIES - Alkali Metals - Alkaline Earth Metals - Transition Metals - Halogen Gases - Inert Gases (Noble Gases) EXAMPLES OF PHYSICAL PROPERTIES - Density - Boiling Point - Melting Point - Conductivity - Heat Capacity EXAMPLES OF CHEMICAL PROPERTIES - Valence electrons - Reactivity - Radioactivity

42 Group 1A: Alkali Metals Hydrogen is a very special element of the periodic table and doesn't belong to any family. While hydrogen sits in Group I, it is NOT an alkali metal. Alkali Metals are found in nature only as compounds. They are highly reactive!!! Least Reactive More reative

43 Group 2A: Alkaline Earth Metals The members of the alkaline earth metals include: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra).

44 Alkaline Earth Metals While not as reactive as the alkali metals, this family knows how to make bonds very easily. Each of them has two electrons in their outer shells. They are ready to give up those two electrons in electrovalent bonds. Sometimes you will see them with two halogen atoms (BeF2) and sometimes they might form a double bond (CaO).

45 Alkaline Earth Metals, cont. The other elements are found in many items including fireworks, batteries, flashbulbs, and special alloys. The lighter alkaline earth metals such as magnesium and calcium are very important in animal and plant physiology. You all know that calcium helps build your bones

46 Group 3A: Boron Family Boron is a Metalloid and is hard and brittle Boron occurs with oxygen, never found in nature by itself It is important in making heat resistant glass Aluminum, Gallium, Indium, and Thallium are all metals

47 Group 4A: The Carbon Family Carbon, Silicon, Germanium, Tin, & Lead Carbon the basis for organic compounds Silicon is the 2 nd most abundant element found in the Earth s crust. It is used in glass making, computer chips, and solar cells

48 Group 5A: Nitrogen Family Contains 2 nonmetals: Nitrogen & Phosphorus (often used in fertilizers) Contains 2 metalloids: arsenic & antimony Contains 1 metal: bismuth

49 Group 6A: Oxygen Family 3 nonmetals: oxygen, sulfur, & selenium 2 metalloids: tellurium & polonium Have 6 valence electrons

50 Group 7A: Halogens The elements included are Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). When a halogen combines with another element, the resulting compound is called a halide. One of the best examples of a halide is sodium chloride (NaCl)

51 Halogens Have 7 valence electrons Readily bonds with group 1A Highly reactive non-metals, fluorine is the most reactive

52 Properties of Halogens

53 Group 8A: Noble Gases (Inert) Group 8A Usually colorless, odorless, and nonreactive

54 Transition Metals Transition metals are good examples of advanced shell ideas. They have a lot of electrons and distribute them in different ways.

55 Transition Metals Rules Transition metals are able to put more than eight electrons in the shell that is one in from the outermost shell. Think about argon (Ar). It has 18 electrons set up in a order. Scandium is only 3 spots away with 21 electrons, but it has a configuration of Wow! This is where it starts. This is the point in the periodic table where you can place more than 8 electrons in a shell

56 Ionization Energy

57 Ground State When all of the electrons in an atom have the lowest possible energy it is in ground state. This is the most stable for that element

58 Name that Element

59 Name That Element