Unit 4: Atoms and the Periodic Table. (with adaptations by J. Stevens)

Transcription

1 Unit 4: Atoms and the Periodic Table (with adaptations by J. Stevens)

2 Vocabulary Atom Term Definition Example Building blocks of matter Proton Neutron Electron Nucleus Valence Electron Subatomic particle with positive () charge; located in nucleus of atom; determines identity of element Subatomic particle with no charge, located in the nucleus of the atom Subatomic particle with negative charge; much smaller than protons and neutrons Center of atom; made of protons and neutrons Electron found in outermost shell of an atom; determines atoms chemical properties

3 Vocabulary Term Definition Example Atomic Number Mass number Number of protons in the nucleus of an atom Protons neutrons Atomic Mass Isotope Ion Bohr Model Lewis Dot Structure ph scale Weighted average of masses of isotopes of each atom Atom with same # of protons as other atoms of that element, but different # of neutrons An atom that has gained or lost one or more electrons; thus having a or charge Model used to visualize atomic structure Used to show number of valence electrons in an atom Scale used to show acidity or alkalinity of something.

4 Vocabulary Term Definition Example Acid Compound which increases H ions when dissolved in H2O Base Compound which increases hydroxide ions (OH) when dissolved in H2O Gravitational Force Attraction of objects due to their masses and distance; weakest force Electromagnetic Force Weak Nuclear Force Like charges repel and opposite charges attract; Holds electrons around the nucleus Force responsible for radioactive decay. Strong Nuclear Force Holds the atomic nucleus together; Counteracts the electromagnetic force

5 Vocabulary Term Definition Example Periodic Table Group Period Metals Nonmetals Metalloids Table where elements are arranged by increasing atomic number Vertical (up and down) column of periodic table; elements in group share chemical properties (same # valence electrons) Horizontal row of elements in periodic table; = how many orbitals atoms have Good conductors of heat and electricity; to left of stair step usually gases or brittle solids at room temp; are poor conductors; to right of stair step Have characteristics of metals and nonmetals; make up stair step

6 Vocab: Atom Valence Electron Ion Proton Atomic Number Bohr Model Neutron Mass Number Lewis Dot Electron Atomic Mass ph scale Nucleus Isotope Acid Base Section 1: Atomic Structure (with adaptations by J. Stevens) Key Ideas: Know the structure of atoms Explain how subatomic particles are different in terms of mass, electrical charges, and location in the atom Understand Hydrogen ion concentration in acids and bases, and how the ph scale measures acids and bases

7 How small are atoms? hnn0i If they are so small, how do we know they exist?

8 Demonstration Cutting paper in half. Then in half again. And again. And again How many times do I have to cut to get to the size of an atom? You would have to cut the paper in half around thirtyone (31) times to get to the size of any atom.

9 1700s 1800s 1900s History of the Atom Timeline Antoine Lavoisier makes J.J. a substantial Thomson number discovers of contributions the to the electron field of and Chemistry proposes the Plum Pudding Model in Niels Bohr proposes the Bohr Model in James Chadwick discovered the neutron in in BC 0 Democritus proposes the 1 st atomic theory Erwin John Dalton Ernest Rutherford Schrodinger proposes performs his the Gold Foil describes atomic theory Experiment in in 1909 the electron 1803 cloud in Click on picture for more information

10 History of the Atom For thousands of years, many scientists have been trying to figure out what makes up all matter? Of course, its atoms. But what are they made of? What do they look like? How do they work? After many scientists contributions, and many experiments, we now have a model (the Electron Cloud model), that is supported by all previous evidence

11 Progression of the Atomic Model Electron Cloud The structure of an atom, according to: James Ernest Erwin J.J. Democritus Neils Schrodinger Chadwick Thomson Rutherford Bohr & John Dalton

12 Image taken from: chemistry.wikispaces.com/1 1TheAtom

13 Where are we now? Watch The existence of quarks Existence of Quarks Watch A boy and his atoms hatoms.shtml#fbid=kt4y4qgwgbx Scanning Tunneling Microscope r_embedded&v=rnfa3m6hvo

14 The Building Blocks of Matter: Atoms

15 Matter Anything that has mass and takes up space (volume) Examples: A brick has mass and takes up space A desk has mass and takes up space A pencil has mass and takes up space Air has mass and takes up space All of the above examples are considered matter because they have mass and take up space. Can you think of anything that would not be considered matter?

16 What are atoms made of? For example, what is the smallest possible unit into which a long essay can be divided and still have some meaning? Smallest possible unit into which matter can be divided, while still maintaining its properties. Made up of: protons neutrons electrons The solar system is commonly used as an analogy to describe the structure of an atom

17 Atoms are so small that it would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen. if you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter about the size of a pingpong ball a human hair is about 1 million carbon atoms wide. a typical human cell contains roughly 1 trillion atoms. a speck of dust might contain 3x10 12 (3 trillion) atoms.. it would take you around 500 years to count the number of atoms in a grain of salt. CCCCC 999,995 more 1 trillion atoms Is made of approximately 3 trillion atoms Just one of these grains

18 Protons () Positively charged particles, in the nucleus # protons = atomic number Contribute to the atomic mass # protons = to # of electrons (in a neutral atom) Help identify the atom (could be considered an atom s DNA)

19 Neutrons Neutral particles; have no electric charge In the nucleus Contribute to the atomic mass Found by subtracting the number of protons from the mass number Mass number protons= neutrons

20 Electrons () Negatively charged particles Found outside the nucleus of the atom, in the electron orbits/levels; each orbit/level can hold a maximum number of electrons ( 1 st = 2, 2 nd = 8, 3 rd = 8 or 18, etc ) Move so rapidly around the nucleus that they create an electron cloud Mass is insignificant when compared to protons and neutrons (smallest) = to number of protons (in a neutral atom) Involved in the formation of chemical bonds

21 Valence Electrons Number of electrons in the outside orbital of the atom Electrons that can be gained, lost or shared in chemical reactions and chemical bonding How many valence electrons does this atom have? What element is this atom?

22 Bohr Model Even though this model is not correct, we use it to easily visualize what is happening with protons, neutrons and electrons. How do we know that this model is Nitrogen? atomicmodel

23 Lewis Dot Structure Lewis Dot Structure shows the number of valence electrons for atoms. How many valence electrons does this atom of Nitrogen have? How many total electrons does it have? Dot.GIF

24 Hydrogen (H) Atom Notice the one electron in the first orbital = 1 = 0 = 1 How many more electrons can fit in the 1 st orbital/ level?

25 Oxygen (O) Atom Notice the two electrons in the first orbital/level and the six in the second = 8 = 8 = 8 How many more electrons can fit in the 2 nd orbital/ level?

26 Sodium (Na) Atom Notice the two electrons in the first orbital/level, eight in the second, and one in the third = 11 = 12 = 11

27 The Atom s Center Protons and neutrons are grouped together to form the center or nucleus of an atom. Notice that the electrons are not apart of the nucleus

28 QUARKS Particles that make up protons and neutrons Existence of Quarks Notice the smaller particles that make up this neutron after you take a closer look. Notice the smaller particles that make up this proton after you take a closer look. What do you notice about the number of quarks in the neutron and proton?

29 SubAtomic Particles Weight Comparison (protons, neutrons, electrons) Neutron = x10 27 kg Proton = x10 27 kg Electron = x10 31 kg 1839 electrons = 1 neutron 1836 electrons = 1 proton How do you think the mass of a neutron compares to that of a proton? 1 neutron 1 proton

30 Subatomic Particles Size Comparison (protons, neutrons, electrons, & quarks) Size in atoms Size in meters (m) Atom Nucleus Proton or Neutron Electron or Quark 1 10, , ,000, (at largest)

31 Atomic Numbersame as the number of protons The number of protons in the nucleus of an atom What would be the atomic number of this atom?

32 Mass Number (protons neutrons) Tells us the number of protons and neutrons in an atom s nucleus Expressed in Atomic Mass Units (amu) Each proton or neutron has a mass of 1 amu What would be the mass number of this atom? protons 4 neutrons = a mass number of 7 amu Why did we not account for the electrons when calculating the mass number?

33 Let s Practice Building Atoms What are the atomic and mass numbers (amu) for the following atoms? Atoms Protons Neutrons Electrons Carbon Beryllium Oxygen Lithium Sodium

34 Average Atomic Mass The weighted average of the masses of all the naturally occurring isotopes of an element (forms of an element with different number of neutrons) The average considers the percent abundance of each isotope in nature Found on the periodic table of elements Example What would be the atomic mass ( ) of Hydrogen if these three isotopes were found in the following percentages (99.9, 0.015, 0) respectively? Hydrogen (Protium) Mass # = 1 amu Hydrogen (Deuterium) Mass # = 2 amu Hydrogen (Tritium) Mass # = 3 amu If you simply average the three, 2 amu (1 amu 2 amu 3 amu/3) would be the atomic mass, but since 99.9% of the Hydrogen is Protium, the atomic mass is around 1 amu (.999 x 1 amu)

35 Ion Atom that does not have the same number of electrons and protons, resulting in either a or charge If I gain electrons, I get a negative charge (more electrons than protons) If I lose electrons I get a positive charge (more protons than electrons) Now Currently, that three this this atom electrons atom of of oxygen oxygen were just lost, is gained the neutral number an because electron, of electrons it it has is an no (6) equal longer and number neutral protons of or (8) electrons an is atom. still (8) unbalanced; It and is protons now considered therefore, an it is ion still (anion). ion, This but ion now has it is more specifically electrons referred (9) than to protons as a cation. (8). = 8 = 8 = 96 8 (8). Symbol = O 2 1

36 Building Ions Build the following ions, and determine their atomic and mass numbers. Ions Protons Neutrons Electrons Carbon (C³ ) Hydrogen (H¹) Oxygen (O² ) Lithium (Li³) Sodium (Na¹ ) Be aware that the atomic and mass numbers are not impacted by the loss or gain of electrons.

37 Acids and bases The ph scale potential hydrogen

38 Acids and Bases Acid Releases a hydrogen ion (H) when it dissolves in water. 0 to 7= acids strong weak Examples: lemon juice, hydrochloric acid (in our stomachs) Taste sour, burns nose, sticky Base Removes H ions from a solution 7 to 14= basic weak strong Examples: household cleaners Taste bitter, usually no smell, slippery ***ph of 7 is neutral neither acid or base, like water

39 Atoms in Review

40 Section 2: FORCES IN THE ATOM Key Ideas: Understand the magnitude and range of the four fundamental forces Recognize the effect of each force on the structure of matter Vocab: Gravitational Force Electromagnetic Force Strong Nuclear Force Weak Nuclear Force

41 Section 2: FORCES IN THE ATOM Gravitational Force Electromagnetic Force Weak Nuclear Force Strong Nuclear Force Nature of Forces

42 Gravitational Force Attraction of objects due to their masses and distance The amount of gravity between objects depends on their masses and the distance between them Weakest Force Do you think this force plays a significant role in holding the atom together?

43 Electromagnetic Force Like charges repel and opposite charges attract Holds electrons around the nucleus Gravity and Electromagnetism Notice how the particles with the same charge move apart and the particles with different charges move together. Why are neutrons not pictured above?

44 Strong Force Holds the atomic nucleus together Counteracts the electromagnetic force Weak and Strong Nuclear Forces How does a particle accelerator work? Particle Accelerator If you need help remembering strong force, just think of Notice how the electromagnetic force causes the protons to repel each other but, the strong force holds them together. Would an atom have a nucleus if the strong force did not exist?

45 Weak Nuclear Force This force plays a key role in the possible change of subatomic particles. For example, a neutron can change into a proton() and an electron() The force responsible for radioactive decay. Radioactive decay process in which the nucleus of a radioactive (unstable) atom releases nuclear radiation. Notice how the original particle changes to something new. n If you need help remembering weak force, just think of

46 Key Ideas Section 3: The Periodic Table Relate the properties of atoms and their position in the periodic table to the arrangement of their electrons Vocab Periodic Table Group Period Metal NonMetal Metalloids

47 What is the periodic table of elements?

48 What is the periodic table of elements? Table where elements are organized by increasing atomic number (or number of protons) Nova Interactive Periodic Table

49 First Organizers Dmitri Mendeleev (late 1800 s), Russian chemist Organizes first periodic table based on atomic mass, but some elements are out of order Henry G.J. Moseley (1913), British chemist Arranged elements by atomic number, which is what we use today Student of Rutherford

50 How is the periodic table actually organized? Groups: Vertical columns of elements with similar properties Numbered 1 18 Elements in same group, have the same number of electrons in outer energy level (valence electrons) Example: Every element in group 1, has 1 electron in its outer shell, every element in group 2, has 2 electrons in its outer shell, and so on (excluding transition metals)

51 Valence Electrons Electrons in the last shell or energy level of an atom Important because: Determine an elements ability to bond with another element Chemical properties depend almost entirely on the configuration of the outer electron shell (reactivity, flammability, etc.)

52 How is the periodic table actually organized? Periods Horizontal rows of elements that contain increasing numbers of protons and electrons Numbered 1 7 Each row in a period ends when an outer energy level is filled Example: Every element in the top row has 1 orbital for its electrons, 2 nd row has two orbitals and so on

53 How is the periodic table actually organized? Categorized by: Alkali Alkaline Earth Transition Metals Basic metal Semi metal Nonmetal Halogens Noble Gas Lanthanide (rareearth) radioactive Actinides (rareearth) radioactive

54 3 Main categories Table/periodic_table.JPG Metals, Nonmetals and Metalloids (Semi Metals)

55 Metals Good conductors of heat and electricity All but Mercury are solid at room temp ***Metals are located to the left of the stair step Alkali Metals (Group 1) are the most reactive of all metals; don t occur in nature in their element form Alkaline Earth Metals (Group 2) shiny, ductile and malleable; combine readily with other elements Transition Metals (Group 3 12) most familiar metals because they often occur in nature uncombined Inner Transition Metals Lanthanide Series elements with atomic # 5871 Actinide Series elements with atomic #

56 NonMetals Elements that are: usually gases or brittle solids at room temp, are poor conductors ***located to the right of the stair step Noble gases (Group 18) exist as isolated atoms. They are all stable because the outer energy level is filled.

57 Metalloids ***Elements that make up the stair step Have metallic and nonmetallic properties (share characteristics with metals and nonmetals) Part of the mixed groups (groups 13, 14, 15, 16 and 17) which contain metals, nonmetals and metalloids

58 How to read the periodic table

59 Watch Hunting the Elements with worksheet