Modern view of the atom

403 Parts of Atom Nomenclature and Parts of the Atom Dr Fred Omega Garces Chemistry 152 Miramar College 1 403 Atomic Structure and Nomenclature 052015

Modern view of the atom What are the parts of the atom and how are these parts (especially the electrons) arranged in each atom? What makes each atom (element) different from each other? What makes certain atoms (elements) similar to each other? 2 403 Atomic Structure and Nomenclature 052015

Planetary Model 3 5 6 7 8 4 2 Nucleus 1 Niels Bohr (1913) Proposed the first reasonable model of the atom (hydrogen) Model of the Hydrogen atom is liken to the solar system The center is the sun (most heaviest planetary body) Planets are confined to their orbitals Planet orbits the sun The center is the nucleus (most dense) Electrons are located in discrete quantized orbitals electron orbits the nucleus 3 403 Atomic Structure and Nomenclature 052015

Atomic Model Theories From the time of Dalton g Thomson g Rutherford g Bohr g Schrodinger, our model of the atom has undergone many modifications The model is not finish however 4 403 Atomic Structure and Nomenclature 052015

Mass and Volume; Size Nucleus are so dense that the size of the pea has a mass of 250 million tons Protons in nucleus held together by nuclear binding force 5 403 Atomic Structure and Nomenclature 052015

Parts of the atom Relative mass and charge for the subatomic particles of an atom Particle Mass *Rel Mass Rel Charge (amu) e - ; electron 9109 10-31 Kg 1/1837-1602 10-19 C p + ; proton 1673 10-27 Kg 1 + 1602 10-19 C n; neutron 1675 10-27 Kg 1 0 * Relative mass: 1 amu ~ mass of proton 1amu equals exactly one-twelfth the mass of a carbon-12 isotope 6 403 Atomic Structure and Nomenclature 052015

Mass of the Atom; A typical heavy atom ie, lead-208, with 82 protons, 82 electrons and 126 neutrons It has a mass of 35 10-22 g You need 13 10 24 lead-208 to make one pound of lead This number is so large that if distribute this many atom to the citizen of this planet (~5 billion) each would have 26 10 14 atoms If all these atoms where pennies, we all would be trillionires 7 403 Atomic Structure and Nomenclature 052015

The density of the nucleus; The density of the lead-208 nucleus is 18 10 14 g/cc This is an extremely high density To put it in perspective, if a paper clip had this much density, it would weigh over 10-million (10 7 ) tons The Statue of Liberty is about 250 tons, 10,000,000 tons is 40,000 Statues of Liberty!!! http://wwwendexcom/gf/buildings/liberty/libertyfactshtm 8 403 Atomic Structure and Nomenclature 052015

The size of the nucleus; If the nucleus of a lead-208 atom were the size of a golf ball, then the whole atom would be much larger than a Coliseum stadium In fact, it would be a sphere about half-mile in diameter 9 403 Atomic Structure and Nomenclature 052015

Mass of the electron; An electron has a mass of 91 10-28 g The sun is very big, it weigh about 333,000 times as much as the earth The mass of the sun is to the mass of the pineapple as the mass of the pineapple is to the mass of an electron Electron 10 403 Atomic Structure and Nomenclature 052015

Mass of the nucleus; The total mass of the 82 electrons in a lead-208 atom is 75 10-26 g, the mass of the whole atom is only 35 10-22 g (electrons account for only 1/2000 th ) I weigh about 149 lb, my mass is to the mass of the proton as the mass of a nickel is to the mass of an electron 11 403 Atomic Structure and Nomenclature 052015

Size of the Atom; An atom has a diameter of about 35 10-8 cm If you could line them up with the atoms just touching, it would take 73 million (73,000,000) atoms to make a line 1 inch long 12 403 Atomic Structure and Nomenclature 052015

Why are elements so different? (if particles are identical) Electrons dictate chemistry, it is the electron which interact with each other Their arrangement is different for each element which give rise to the element s different properties 13 403 Atomic Structure and Nomenclature 052015

A X chg Nomenclature: Z X - Symbol of element A - Atomic mass = no proton + no neutron Z - Atomic number = no proton, detm' identity chg - charge of atom = sum of no p (+) & no e (-) ( Elements with the same atomic number (Z) but different atomic mass (A) are called isotopes) 14 403 Atomic Structure and Nomenclature 052015

The atoms: Different Elements 1s 2 2 2 12C 6 6 6 14 N 7 7 7 16O 8 8 8 6p +,6n 1s 2 2 3 7p +, 7n 1s 2 2 4 8p +,8n The periodic table give an atomic mass that is not a whole number? ie, C = 12011 amu, H = 1008 amu, O = 159994 amu 15 403 Atomic Structure and Nomenclature 052015

The atoms: Different Elements 1s 2 2 2 12C 6 6 6 14 N 7 7 7 16O 8 8 8 6p +,6n 1s 2 2 3 7p +, 7n 1s 2 2 4 8p +,8n The periodic table give an atomic mass that is not a whole number? ie, C = 12011 amu, H = 1008 amu, O = 159994 amu 16 403 Atomic Structure and Nomenclature 052015

The atoms: Different Elements 1s 2 2 2 12C 6 6 6 14 N 7 7 7 16O 8 8 8 6p +,6n 1s 2 2 3 7p +, 7n 1s 2 2 4 8p +,8n The periodic table give an atomic mass that is not a whole number? ie, C = 12011 amu, H = 1008 amu, O = 159994 amu 17 403 Atomic Structure and Nomenclature 052015

The atoms: Isotopes 12 C 6 6 6 13 C 6 6 7 14 C 6 6 8 1s 2 2 2 1s 2 2 2 1s 2 2 2 Isotopes - atoms with different # of neutrons and protons ie, C-12, C-13 C-14 6p +,6n 6p +, 7n 6p +, 8n 75% of all elements have more than one isotope Titanium and nickel has five isotope, while fluorine and potassium have just one 18 403 Atomic Structure and Nomenclature 052015

The atoms: Isotopes 12 C 6 6 6 13 C 6 6 7 14 C 6 6 8 6p +,6n 1s 2 2 2 1s 2 2 2 6p +, 7n 1s 2 2 2 6p +, 8n Isotopes - atoms with different # of neutrons and protons ie, C-12, C-13 C-14 75% of all elements have more than one isotope Titanium and nickel has five isotope, while fluorine and potassium have just one 19 403 Atomic Structure and Nomenclature 052015

The atoms: Isotopes 12 C 6 6 6 13 C 6 6 7 14 C 6 6 8 6p +,6n 1s 2 2 2 1s 2 2 2 6p +, 7n 1s 2 2 2 6p +, 8n Isotopes - atoms with different # of neutrons and protons ie, C-12, C-13 C-14 75% of all elements have more than one isotope Titanium and nickel has five isotope, while fluorine and potassium have just one 20 403 Atomic Structure and Nomenclature 052015

The atoms: Charge atoms (ions) 14 C 6 6 8 14 C +2 6 4 8 14 C -2 6 8 8 6p +, 8n 1s 2 2 2 1s 2 2 0 6p +, 8n 1s 2 2 4 6p +, 8n ions - charge of atom / isotope or group of atoms (+) cation (cat) (-) anion (ant) 21 403 Atomic Structure and Nomenclature 052015

The atoms: Charge atoms (ions) 14 C 6 6 8 14 C +2 6 4 8 14 C -2 6 8 8 6p +, 8n 1s 2 2 2 1s 2 2 0 6p +, 8n 1s 2 2 4 6p +, 8n ions - charge of atom / isotope or group of atoms (+) cation (cat) (-) anion (ant) 22 403 Atomic Structure and Nomenclature 052015

The atoms: Charge atoms (ions) 14 C 6 6 8 14 C +2 6 4 8 14 C -2 6 8 8 6p +, 8n 1s 2 2 2 1s 2 2 0 6p +, 8n 1s 2 2 4 6p +, 8n ions - charge of atom / isotope or group of atoms (+) cation (cat) (-) anion (ant) 23 403 Atomic Structure and Nomenclature 052015

The atoms: Charge atoms (ions) 14 C 6 6 8 14 C +2 6 4 8 14 C -2 6 8 8 6p +, 8n 1s 2 2 2 1s 2 2 0 6p +, 8n 1s 2 2 4 6p +, 8n ions - charge of atom / isotope or group of atoms (+) cation (cat) (-) anion (ant) 24 403 Atomic Structure and Nomenclature 052015

The atoms: Identifying the element (1) What is the element with the following subatomic particles? 15? 7 X 7 7? 15 N Nitrogen N 1s 2 2 3 7p +, 7n Nitrogen? X? 7 7 7 N 7 14 N Answer 1s 2 2 3 7p +, 7n 25 403 Atomic Structure and Nomenclature 052015

The atoms: Identifying the element (1) What is the element with the following subatomic particles? 15? 7 X 7 7? 14 N Nitrogen N 1s 2 2 3 7p +, 7n 15 X? 7 7 7 8 15 N Nitrogen N 1s 2 2 3 7p +, 8n 26 403 Atomic Structure and Nomenclature 052015

The atoms: Identifying the element (2) What is the specie with the following subatomic particles?? X -2 8? 9 8 17 O -2 Oxygen 1s 2 2 2 O - 2 8p +, 9n 8 8 9 17 X -2 8 17 O -2 Oxygen 1s 2 2 2 O - 2 8p +, 9n 27 403 Atomic Structure and Nomenclature 052015

The atoms: Identifying the element (2) What is the specie with the following subatomic particles? 8-2? 17 X? 8 17 O -2 Oxygen 1s 2 2 2 O - 2 8p +, 9n? X? 8 10 9 8 17 O -2 Answer Oxygen 1s 2 2 2 O - 2 8p +, 9n 28 403 Atomic Structure and Nomenclature 052015

Atomic Nomenclature: Exercise #1 #2 #3 #4 #1 #2 #3 #4 Protons 33 Protons 30 85 34 54 Neutrons 35 125 45 81 Neutrons 35 44 Electrons 28 86 36 54 Electrons 28 36 A (atomic Mass) 65 210 79 135 A (atomic Mass) 113 Z (atomic No) 30 85 34 54 Z (atomic Number) 48 Charge +2-1 -2 0 Charge +2 +2 Symbol 30 65 Zn +2 85 210 At - 34 79 Se -2 135 Xe Symbol 222 Rn 29 403 Atomic Structure and Nomenclature 052015

Atomic Mass: a closer look According to the periodic table the atomic mass of carbon is 120107 amu, chlorine is 35453 amu Yet we just said that the mass of an atom is arrived by the number of protons and neutrons for that atom How is it that we have 011 amu worth of atom Is there such a thing as a fraction of an atom? 30 403 Atomic Structure and Nomenclature 052015

What cost $100? -Song from itunes -Lemonade -Slice of pizza Weighted Average Consider a song from itunes; Not all songs are $100 Suppose you bought 4 songs, $1, $1, $1 and $125 What is the average cost of each? $425 / 4 or $106 here is what you did 1-1 - 1-125 : What is the average 1 + 1 + 1 + 125 = 425 / 4 = 106 or 1 (25) + 1(25) + 1(25) + 125(25) = 25 + 25 + 25 + 31 = 106 This is called the weighted average The values are weighted against its population in the collection 31 403 Atomic Structure and Nomenclature 052015

Weighted Average The mass of the elements from the periodic table is actually the weighted average Consider the following: 8-7 - 6-6 : What is the average 8 + 7 + 6 + 6 = 27: 27 / 4 = 675 or 8 (25) + 7(25) + 6(25) + 6(25) = 2 + 175 + 15 + 15 = 675 Now what is the atomic mass for chlorine which exist in the following abundance: Cl-35 (7553 % ) & Cl-37( 2447 %) At Wt = 35(7553) + 37(2447) = 2644 + 905 = 3549 g/mol 32 403 Atomic Structure and Nomenclature 052015

Atomic Mass Unit What is the mass of an object that cannot be seen? What scale / units of mass is used for such small objects? Unit of mass that is comparable to object of that size atomic mass unit (amu) has been used as a standard for a mass of an atom 1 amu = 166 10-27 Kg = 1/12 mass of 12 C Atoms: Atomic mass one atom of potassium 19 K weighs 19 amu one atom of zinc 30 Zn weighs 30 amu Molecule: Molecular mass one water (H 2 O) molecule 2-H, 1-O = 2amu + 16amu = 18 amu one glucose (C 6 H 12 O 6 ) molecule: 6C, 12H, 6O = [6 C 12amu] + [12 H 1 amu] + [6 O 16amu] = 144 amu 33 403 Atomic Structure and Nomenclature 052015

Isotopic Distribution Isotopic Distribution: Question comes to mind: Why is the mass of carbon 12011 according the periodic table? Why is the mass of chlorine 35453? That of copper 63546? Is not the mass of an atom reflected on the number of protons and neutrons an atom possesses? If so, is there such a thing as 0011 amu of subatomic proton or neutron for carbon Or 0453 in chlorine and 0546 in copper? Atomic mass, as shown in the periodic table, is the average of all isotope found in nature Atomic mass is the weighted average mass for the isotropic distribution(found in nature) for that element Weighted atomic mass average for the copper atom: Copper has two stable isotope: 63 Cu - 7270 %, and 65 Cu - 2730 % 63 amu (07270) + 65 amu (02730) = 63546 amu 34 403 Atomic Structure and Nomenclature 052015

Summary Piecing together the Atomic Structure 35 403 Atomic Structure and Nomenclature 052015