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COS 1.0, 1.1, 1.2, 1.3

COS 1.0, 1.1, 1.2, 1.3. RECOGNIZE PERIODIC TRENDS OF ELEMENTS, INLCUDING THE NUMBER OF VALENCE ELECTRONS, ATOMIC SIZE AND REACTIVITY. CATEGORIZE ELEMENTS AS METALS, NONMETALS, METALLOIDS AND NOBLE GASES. DIFFERENTIATE BETWEEN FAMILIES AND PERIODS.

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COS 1.0, 1.1, 1.2, 1.3

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  1. COS 1.0, 1.1, 1.2, 1.3 • RECOGNIZE PERIODIC TRENDS OF ELEMENTS, INLCUDING THE NUMBER OF VALENCE ELECTRONS, ATOMIC SIZE AND REACTIVITY. • CATEGORIZE ELEMENTS AS METALS, NONMETALS, METALLOIDS AND NOBLE GASES. • DIFFERENTIATE BETWEEN FAMILIES AND PERIODS. • USE ATOMIC NUMBER AND MASS NUMBER AND MASS NUMBER TO IDENTIFY ISOTOPES.

  2. WHAT YOU’LL LEARN • State the charge, mass, & location of each part of an atom according to the modern model of the atom. • Relate the organization of the periodic table to the arrangement of electrons within an atom. • Identify isotopes of common elements. • Determine how many protons, neutrons, & electrons an atom has, given its symbol, atomic number, & mass number. • Locate alkali metals, alkaline earth metals, & transition metals in the periodic table. • Locate semiconductors, halogens, & noble gases in the periodic table.

  3. ATOMIC STRUCTURE

  4. WHAT ARE ATOMS? • smallest part of an element that still has element’s properties. • building blocks of molecules

  5. WHAT’S IN AN ATOM?

  6. NUCLEUS • center of each atom • small & dense • has positive electric charge

  7. PROTONS • subatomic particle that has positive charge • found in nucleus

  8. NEUTRONS • subatomic particle that has no charge • no overall charge • equal number of protons and electrons whose charges exactly cancel

  9. ELECTRONS • subatomic particles with negative charges. • located in a cloud (orbit) moving around outside nucleus

  10. QUARKS • particles of matter that make up protons and neutrons

  11. MODELS OF THE ATOM

  12. DEMOCRITUS • Greek philosopher • developed theory around 400 B.C. • proposed that atoms make up all substances • Atom — “unable to be divided”

  13. JOHN DALTON • Developed atomic theory in 1808 • first atomic theory with a scientific basis • model was simple sphere • thought the atom could not be split • Atoms of same element exactly alike

  14. NIELS BOHR • theory developed in 1913 • suggested that electrons in an atom move in set paths around the nucleus much like planets orbit sun It is impossible to determine an electrons: • exact location • speed • direction Best scientists can do is: • calculate chance of finding an electron in a certain place within an atom

  15. J.J. Thomson (1897) • Discovered negatively charged particles • atom was divisible! • Particles discovered are electrons • Atom consists of positively charged material with negative charges spread evenly throughout

  16. Rutherford (1908) • Gold Foil Experiment • Positive particles shot at gold foil occasionally bounced back! • Proposed dense, positively charged center called the nucleus

  17. ENERGY LEVELS • path of a given electron's orbit around a nucleus, marked by a constant distance from the nucleus • Closer to nucleus, lower energy level of electrons • Further from nucleus, more energy electrons have • Number of filled energy levels an atom has depends on number of electrons

  18. ORBITAL • region in an atom where there is a high probability of finding electrons

  19. VALENCE ELECTRONS • found in outermost shell of an atom • determines atom’s chemical properties • participate in chemical bonding • Every atom has between one and eight

  20. THE PERIODIC TABLE

  21. ORGANIZATION OF THE PERIODIC TABLE • Groups similar elements together • organization makes it easier to predict properties of an element based on where it is in periodic table • Elements are listed in order of number of protons

  22. PERIODIC LAW • states that when elements are arranged this way, similarities in their properties will occur in a regular pattern • helps determine electron arrangement

  23. PERIODS • Horizontal rows • number of protons & electrons increases as you move from left to right

  24. FAMILY/GROUP • vertical column of elements • Atoms of elements in same group have same number of valence electrons • elements have similar properties

  25. IONS • an atom or group of atoms that has lost or gained one electron and has a negative or positive charge

  26. HOW THE STRUCTURES OF ATOMS DIFFER

  27. ATOMIC NUMBER (Z) • number of protons in the nucleus

  28. MASS NUMBER (A) • number of protons plus the number of neutrons in nucleus

  29. ATOMIC RADIUS • is size of atom GROUPS • radius increases as one proceeds down any group of periodic table WHY? • adding layers of electrons PERIODS • radius decreases as one proceeds across any row of periodic table WHY? • increasing number of protons in nucleus as you go across the period pulls electrons in more tightly.

  30. ISOTOPE • has same number of protons as other atoms of same element do but has a different number of neutrons. • Some are more common than others. • If you know the atomic number and mass number of an atom, you can calculate the number of neutrons it has.

  31. Example Chlorine 35 has a mass number of 35. Has an atomic number of 17. • Mass number (A): 35 • Atomic number (Z): –17 • Number of neutrons: 18

  32. ATOMIC MASS UNIT (amu) • Mass of an atom or molecule that is exactly 1/12th the mass of a carbon atom with mass number 12

  33. AVERAGE ATOMIC MASS • weighted average of masses of all naturally-occurring isotopes of an element

  34. Avg. Atomic Mass AVERAGE ATOMIC MASS EXAMPLE • About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37. 35.4 u

  35. FAMILIES OF ELEMENTS

  36. HOW ARE ELEMENTS CLASSIFIED? • By similar physical & chemical properties.

  37. ALKALI METALS • group 1 • shiny • malleable • ductile • React violently w/ water • Very reactive b/c it has only one valence electron • Has +1 charge • Not found in nature as elements • Found only in compounds • Ex: salt (NaCl) Lithium • used to treat bipolar disorder

  38. ALKALI EARTH METALS • Group 2 • two valence electrons • +2 charge • shiny • malleable • ductile • Form compounds in stone & human body Calcium (Ca): • Shells of sea animals, coral reefs (limestone), skeletal structure humans … Magnesium (Mg) • Air plane construction • Activates enzymes that speed up processes in humans • brilliant white color in fireworks Medicines • milk of magnesia • Epsom salt

  39. TRANSITION METALS • groups 3-12 • most familiar • found in elemental state Iron • most abundant metal • used in steel Aluminum • making containers, automotive parts, cookware… MERCURY • only metal at room temperature • used in thermostats, thermometers, batteries …

  40. NONMETALS • Some elements found in groups 13-16 & all elements in groups 17-18 • except hydrogen • usually gases or brittle solids at room temperature • poor conductor of heat & electricity • may be solids, liquids, or gases at room temperature.

  41. HALOGENS • Group 17 • very reactive in elemental state Chlorine • greenish yellow gas • Kills bacteria • Elemental chlorine is very poisonous • obtained from seawater Fluorine • Poisonous yellow gas • used in toothpaste Bromine • Dark red liquid • only nonmetal liquid at room temperature • obtained from seawater Iodine • shiny, purple-gray solid • Used as disinfectant • obtained from seawater

  42. NOBLE GASES • group 18 • Exist only as single atoms instead of molecules • Unreactive b/c orbitals are full of electrons Neon • Signs Helium • Less dense than air • Gives lift to blimps & balloons Argon/Krypton • Used in light bulbs

  43. SEMICONDUCTORS • elements that can conduct electricity under certain conditions • Aka metalloids: • Composed of only six elements • Boron, silicon, germanium, arsenic, antimony & tellurium Boron • Extremely hard • Added to steel to increase hardness & strength at high temperatures. Antimony • Used as fire retardants Silicon • Makes up 28% of earths crust • Sand most common compound • Used in electronics

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