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Chapter 3 Atoms and the Periodic Table

Chapter 3 Atoms and the Periodic Table. Reactivity. Groups reactivity METALS As orbits are added the electrons move further away from nucleus and become easier to lose , thus as you move down the group the elements become more reactive

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Chapter 3 Atoms and the Periodic Table

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  1. Chapter 3 Atoms and the Periodic Table

  2. Reactivity • Groups reactivity METALS • As orbits are added the electrons move further away from nucleus and become easier to lose , thus as you move down the group the elements become more reactive • Nonmetals need electrons therefore the elements closer to the nucleus are more capable of accepting electrons and the elements moving up the group become more reactive

  3. More information • Elements moving from left to right in a period becoming smaller due to the pull of the nucleus. • Elements moving down a group become larger in size due to adding orbits • The most reactive families have fewer electrons to lose or gain, therefore groups 1 and 17, why not 18? • Group 2 more reactive than 3 ;;group 16 more reactive than 15

  4. Gases on periodic table • All of 18 are gases known as the noble gases • Other gases that are found naturally • H, N, O, F, Cl, • When these gases appear by themselves they are written as diatomic gases

  5. What are Atoms? defined - are tiny units that determine the properties of all matter an atom is the smallest part of an element that still has the element's properties

  6. introduction Democritus Greek philosopher lived in the 4th century B.C. suggest that the universe made of invisible units called atoms defined - Greek word meaning "unable to divide" believed that the changes he observed was due to the movement of the atoms unable to provide the evidence needed to convince people that atoms existed

  7. Atoms are the building blocks of molecules John Dalton atomic theory in 1808 English school teacher widely supported due to supporting evidence three parts every element is made of tiny unique particles called atoms that cannot be subdivided atoms of the same element are exactly alike atoms of different elements can join to form molecules

  8. What is in an atom? introduction less than a 100 years after Dalton published his atomic theory scientist determined that atoms could be split further today we know there are many different parts of an atom but only three are used in everyday chemistry of most substances In the nucleus - dense center of the atom protons - 1 positive charge with a mass of 1 amu (atomic mass unit) neutrons - 0 charge (neutral) with a mass of 1 amu Electron cloud - made of very tiny moving particles electrons - 1 negative charge with very little mass 0 amu

  9. Atoms have no over all charge because they have an equal number of protons and electrons example He (helium) atom 2 protons 2 neutrons 2 electrons charge of 2 protons +2 charge of 2 neutrons 0 charge of 2 elections -2 total charge 0

  10. Models of the Atom introduction like most scientific models and theories the model of the atom has been revised many time to explain each new discovery Bohr's model Niels Bohr - Danish scientist in 1913 electrons move in set paths around the nucleus like the planets orbit the sun each electron has a certain energy that is determined by its path around the nucleus energy level the path of the possible energies an electron may have in an atom electrons must gain energy to move to a higher energy level

  11. Modern theory by 1925 Bohr's model no longer explained all observations electrons no longer moved in definite paths electrons behave like waves vibrating on a string than like particles impossible to determine the exact location, speed, and direction like a fan blade try to determine location by shading the darker the shading the better the chance to find an electron the whole shaded region is called an electron cloud

  12. electrons are found in an orbital within each energy level (orbit or shell) orbital - the region in an atom where electrons are found exist only when an electron occupies it four different kinds of orbitals "s" orbital simplest shaped like a sphere only 1 orbital or orientation per orbit can contain 2 electrons maximum

  13. "p" orbitals dumbbell shaped 3 different orbitals or orientations per orbit x, y, and z axis 2 electron in each orbital 6 electrons maximum

  14. "d " orbitals 5 possible orbitals or orientations per orbit 2 electrons each orbital 10 electrons maximum "f " orbitals 7 possible orbitals or orientations per orbit 2 electrons each orbital 14 electrons maximum

  15. electrons start off occupying the lowest level then are added to the next highest energy level or orbit 1st energy level or orbit contains only the "s" orbital 2 electrons maximum

  16. 2nd energy level or orbit contains "s" orbital 2 electrons maximum "p" orbitals 6 electrons maximum 8 electrons maximum for the energy level 2 in the s and 6 in the p

  17. 3rd energy level or orbit contains "s" orbital 2 electrons maximum "p" orbitals 6 electrons maximum "d " orbitals 10 electron maximum 18 electrons maximum for the energy level 2 in the s, 6 in the p, and 10 in the d

  18. 4th energy level contains "s" orbital 2 electrons maximum "p" orbitals 6 electrons maximum "d " orbitals 10 electrons maximum "f " orbitals 14 electrons maximum 32 electrons maximum for the energy level 2 in the s, 6 in the p, 10 in the d, and 14 in the f

  19. every atom has one or more valence electrons valence electron - is an electron in the outer most energy level of an atom hydrogen has 1 valence electron (the least number) neon has 8 valence electrons (the maximum number)

  20. Page 76 Questions 1-7 Write questions and answers

  21. 3.2 A Guided Tour of the Periodic Table • Objectives • Relate the organization of the periodic table to the arrangement of electron within an atom. • Explain why some atoms gain or lose electrons to form ions. • Determine how many protons, neutrons, and electrons an isotope has, given its symbol, atomic number, and mass number. • Describe how the abundance of isotopes affects and element’s average atomic mass.

  22. Historical prospective Developed by Dimitri Mendeleev Russian chemist in 1869 based on repeating properties and atomic mass he arranged the known elements and left blank spaces for unknown elements Henry Mosley the first to group atoms by protons

  23. Organization of the Periodic Table similar elements grouped together makes it easier to predict the properties of an element based on where it is in the periodic table elements represented by their symbols order based on the number of protons the atom has in its nucleus Hydrogen has one proton and is the first elements listed in the Periodic Table

  24. Period law properties of elements tend to change in regular pattern when elements are arranged in order of increasing atomic number, or number of protons in their nucleus atomic numbers equals the number of protons increases from left to right and top to bottom

  25. Using the Periodic Table to determine electronic arrangement Periods horizontal rows 1-7 indicates the outer most energy level Period 1 2 elements - H and He has only 1 s orbital maximum of 2 electrons

  26. Period 2 starts with Li and ends with Ne contains 1 s and 3 p orbitals Period 3 starts with Na and ends with Ar contains 1 s and up to 3 p orbitals Periods 4 and 5 contains 1 s and up to 3 p and 5 d orbitals Periods 6 and 7 contains 1 s and up to 3 p, 5d, and 7 f orbitals

  27. Groups vertical columns 1-18 have similar properties have the same number of valence electrons

  28. Groups 1 and 2 electrons are going in the s orbital Group 1 H down to Fr only one electron in the outer most energy level 1 electron in the s orbital these elements have 1 valence electron Group 2 Be down to Ra 2 electrons in the outer most energy level 2 electrons in the s orbital and it is now full these elements have 2 valence electrons

  29. Groups 13 to 18 are placing electrons in the p orbitals of the outer most energy level these elements have 3 to 8 valence electrons Group 13 elements have 3 valence electrons Group 18 elements have 8 valence electrons this is the maximum number of valence electrons the p orbitals are full Valence electrons equals the last digit of the Group number Groups 3 to 12 are placing electrons in the d orbital of the next lower energy level they have 2 valence electrons as far as this class is concerned

  30. The Lanthanoid Series and Actinoid Series are placing electrons in the f orbital of the energy level 2 place back they have 2 valence electrons as far as this class is concerned Atoms in Group 18 have full outer energy levels 8 is the maximum for an outer level except for level 1 He has 2 non reactive (inert)

  31. united video Elements of Chemistry: The Periodic Table (20:00 min.) http://www.unitedstreaming.com/search/assetDetail.cfm?guidAssetID=F59A819C-DB1B-48E6-90D7-DF3829C74230

  32. Elements are reactive because their outer most energy levels are only partially filled. Some Atoms Form Ions Ionization defined - atoms that may gain or lose valence electrons so that they have a full outermost energy level no longer the same number of protons and electrons it has a net electrical charge

  33. ion defined - an atom or group of atoms that has lost or gained one or more electrons and therefore has a net electric charge cation defined - an ion with a positive charge example: Li has 1 valence electron 2 electrons in the 1st energy level 1 electron in the 2nd energy level when the valence electron is removed Li becomes a positive ion Li+

  34. Li+ ionLi atom3 protons +3 3 protons +32 electrons -2 3 electrons -3 charge +1 0 the other elements in Group 1 form +1 cations by having only one valence electron

  35. anion defined - an ion with a negative charge example: F has 7 valence electrons 2 electrons in the 1st energy level 7 electrons in the 2nd energy level easier to gain 1 electron than lose 7 electrons to become a negative ion. F- ionF atom 9 protons +9 9 protons +910 electrons -10 9 electrons -9charge - 1 0 the other elements in Group 17 form -1 anions by having 7 valence electrons

  36. How Do the Structures of Atoms Differ Atomic number defined - the number of protons in the nucleus of an atom remember atoms are always neutral because they have equal number of protons and electrons the simplest atom H has only 1 proton and 1 electron atomic number is 1 the largest naturally occurring atom U has 92 protons and 92 electrons atomic number is 92

  37. Mass number defined - the total number of protons and neutrons in the nucleus of an atom F has 9 protons and 10 neutrons for a mass number (A) = 19 the mass number can vary from atom to atom of the same element

  38. Isotopes defined - atoms having the same number of protons but different number neutrons example: H has 2 isotopes the first is the protium the atom of H (the most common) has only one proton and 0 neutrons a mass number of 1

  39. the second isotope is Deuterium sometimes called "heavy Hydrogen" 1 proton and 1 neutron a mass number of 2 only 1 out of every 6000 H are Deuterium the third isotope is Tritium 1 proton and 2 neutrons mass number of 3 All three are hydrogen, only one proton, but have different masses due to the neutrons.

  40. Calculating the number of neutrons in an atom average atomic mass defined - the weighted average of the masses of all naturally occurring isotopes of an element This is found under the Symbol on the Periodic Table round this number to the nearest whole number subtract the atomic number

  41. example: C average atomic mass 12.011 = 12 mass number atomic number- 6number of neutrons 6 this is for the most common Carbon atoms (carbon - 12) the isotopes for C will be those with different number of neutrons like carbon - 14 Mass number 14atomic number - 6neutrons 8

  42. Rules for Electron configuration Find the total number of electrons (atomic number). Find the number of energy levels (the period number). Draw the orbits

  43. Find the electrons in the last energy level. For Groups 1& 2 use the Group number. For Groups 13 - 18 use the last digit of the Group number (3 - 8). For He always 2 electrons. For Group 3 - 12 assign 2 electrons Subtract the electrons from the total as you place them in their energy level. Fill in the inner energy levels with the remainder of the electrons starting with the first energy level.

  44. Use the following pattern when they are the inner energy levels. 1st energy level - 2 electrons 2nd energy level - up to 8 electrons 3rd energy level - 8 or 18 electrons 4th energy level - 8, 18, or 32 electrons 5th energy level - 8, 18, or 32 electrons 6th energy level - 8 or 18 electrons Remember to subtract as you add them to their energy levels. Examples: Br K and Bi

  45. Page 85 Questions 1-7 Questions and answers

  46. 3.3 Families of Elements • Objectives • Locate alkali metals, alkaline-earth metals, and transition metals in the periodic table. • Locate semiconductors, halogens, and noble gases in the periodic table. • Relate an element’s chemical properties to the electron arrangement of its atoms.

  47. Groups are sometimes called families each is unique yet share certain similarities elements have common chemical and physical properties they have the same number of valence electrons

  48. How elements are classified Metals the majority of all elements most are solids luster - shiny ductile - can be stretched malleable - can be shaped good conductors of heat and electricity form cations only

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