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Whats it all about?

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The Basic Atom Smallest particle of an element that still has the elements properties Atomic Theory explains what atoms look like, and how and why they behave the way they do Democritus (400 BC) proposed the existence of atoms (philosophy) John Dalton (1800) was the first to have scientific evidence to support this Considered the Father of Modern Atomic Theory

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Daltons Atomic Theory Daltons experiments showed him several things about the existence of atoms he had 5 postulates All matter is made of atoms Atoms are small, indestructible spheres Atoms of the same element are identical Atoms always combine in compounds in whole number ratios In chemical reactions atoms are combined, separated or rearranged

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Daltons Model Daltons idea of the atom was a small sphere hence The Marble Model

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Current model building blocks of matter Charge: Neutral (no charge) particles made up of 3 subatomic particles in 2 regions Electron Cloud: Diffuse (spread out very thinly) Negatively charged area outside of the nucleus Electrons (e - ): o each has a (-1) charge o little mass (0 amu) o located outside of the nucleus Nucleus Tiny Positively charged Dense mass in the atoms center has 2 particles (p + ) protons o each has a (+1) charge o has a mass of 1 a.m.u.* (n) Neutrons o no charge o has a mass of 1 a.m.u.* *a.m.u. = atomic mass unit

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- 0 Region & Particle Relationship Atoms Electron Cloud Charge Balance Subatomic Particle Region Charge Nucleus Neutron Proton electron +

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The Electron

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The Electron Fun Facts Abbreviated e - Gives the electron cloud its charge Gives the element its chemical properties Structure: Lepton (fundamental particle not made of smaller particles) Mass = 0 amu* (amu = atomic mass unit) Not really 0 but 1/1200-1/2000 th the mass of a proton) Charge: negative (exactly balances the p + positive charge) Location: Electron Cloud

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The Electron on the Periodic Table How many electrons are there in an element?? Where do you find it??? 20 Ca Calcium 40.078 # of e - = Atomic Number but only in a neutral atom Lets make a note on our PT & test each other

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The Electron History/Theory Discovery #: 1 st subatomic particle discovered Discovered by JJ Thomson in 1897 JJ Made a CRT (cathode ray tube) and found that when he shot electricity through it a beam of light appeared The beam of light was affected by magnetic & electric forces (does light do that??) He proposed that it wasnt light but tiny, negatively charged particles he called electrons (btw: he thought the discovery was useless)

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Thomsons Model The atom was Neutral in charge so Most of the atom was a diffuse positively charged goo or matrix Electrons were tiny particles that floated around in the goo. Electrons were very tiny compared to the mass of the atom

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The Thomson Plum Pudding Model 1897 The Plum Pudding Model I prefer the Chocolate Chip Cookie Dough Model negative electrons positive matrix or goo that made up the rest of the atom

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The Proton

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The Proton Fun Facts Abbreviated p + Gives the nucleus a positive charge Gives the element its unique characteristics & identifies the element (# p + is unique to each element Structure: Hadron (composite particle made of smaller particles) Mass = 1 amu* Charge: Positive Location: Nucleus

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The Proton on the Periodic Table How many protons are there in an element?? Where do you find it??? 20 Ca Calcium 40.078 # of p + = Atomic Number Lets make a note on our PT & test each other

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The Proton History/Theory Discovery #: 2 nd subatomic particle discovered Discovered by Ernest Rutherford in 1918 Rutherford first proposed the positive nucleus in 1911 from the Gold Foil Experiment changing the model of the atom again http://www.mhhe.com/physsci/chemistry/essentialch emistry/flash/ruther14.swf http://www.mhhe.com/physsci/chemistry/essentialch emistry/flash/ruther14.swf

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Rutherfords Models The nucleus was Very dense Had most of the mass of the atom Was positive Very, very tiny compared to the entire atom Atoms are mostly empty space The electrons move around the outside of the nucleus Rutherford model nuclear model kind of like a plasma ball w/ a tiny positive nucleus and electrons floating around outside it Discovered the proton later in the first nuclear reaction How tiny? 400 x tinier than this and thats only the nucleus!!! Protons are smaller yet!!!!

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The Rutherford (Nuclear) Models 1911 Model with just a positive nucleus in the center of the electrons 1918 Model with protons making up the nucleus

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The Neutron

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The Neutron Fun Facts Abbreviated n 0 Adds mass to the nucleus Helps hold the nucleus together (prevents proton repulsion from destroying the nucleus) Structure: Hadron (composite particle made of smaller particles) Mass = 1 amu* Charge: Neutral (no charge) Location: Nucleus

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The Neutron on the Periodic Table How many neutrons are there in an element?? Where do you find it??? 20 Ca Calcium 40.078 #n 0 is NOT found on the PT More on this later

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The Neutron History/Theory Discovery #: 3 rd subatomic particle discovered Discovered by James Chadwick (also a student of JJ Thomson) in 1936 (Rutherford said it should be there, Chadwick gave them evidence) Chadwick produced a beam of neutral particles that knocked protons out of paraffin wax https://www.youtube.com/watch?v=HnmEI94URK8 Led to the development of the atomic bomb

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Chadwicks Model Similar to the current model with p+ & n 0 in the nucleus and e- orbiting the nucleus in the electron cloud

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Isotopes & The Neutron

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Isotopes & the Neutron Isotopes: Atoms of the same element with different numbers of neutrons The number of neutrons can be different in an element (thats why there is no neutron number on the PT) The number of neutrons must be calculated for each isotope Example: Magnesium has 3 isotopes Symbol#p + #n 0 #e - 12 Mg - 24 12 13 14 Mg - 25 Mg - 26

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Isotopes & Mass Number Mass number (mass #) is the number of p + & n o in a specific isotope of an element Mass # = #p + + n o or #n o = Mass # - #p + Lets put this on the PT somewhere

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Isotopes & Mass Number #1 How do you know which isotope you have?? Mass # is found in one of 2 ways prioritized list 1.Isotope Notation (given to you with the element symbol) 100% accurate C-14 Mass #Element Symbol So in C-14 there are 6 p + & 6 e - (atomic number of C is 6) 8n 0 (Mass # - # p + = #n 0 or 14 - 6 = 8 ) OR 14 6 C Element Symbol Mass # Atomic #

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Practice Isotope Notation Isotope Symbol # p + #n 0 #e - O-18 N-15 Si-30 Cl-37 K-41 Fe-54 Ni-62 Cu-65 Br-79 8108 787 141614 172017 192219 262826 283428 293629 354435

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Isotopes & Mass Number #2 How do you know which isotope you have?? 2. MCI (most common isotope) 50% accuracy Round the Average Mass to a whole number to get mass # for the m.c.i.Average Mass 20 Ca Calcium 40.078 Average mass = 40.078 amu so. round it and The mass number of the most common isotope is 40 so Ca-40 5 B Boron 10.806 Average mass = 10.806 amu so. round it and The mass number of the most common isotope is 11 so B-11

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Average Mass

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Practice M.C.I. method Isotope Symbol # p + #n 0 #e - O N Si Cl K Fe Ni Cu Br 888 - 16 (avg mass = 15.999) - 14 (avg mass = 14.006) - 28 (avg mass = 28.084) - 56 (avg mass = 55.845) - 39 (avg mass = 39.098) - 35 (avg mass = 35.446) - 59 (avg mass = 58.693) - 64 (avg mass = 63.546) - 80 (avg mass = 79.904) 777 141414 171817 192019 263026 283128 293529 354535

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Sample Formats p+ n 0 p+ n 0 p+ n 0 Carbon - 12Carbon - 13Carbon - 14 6 6 6 6 78 Isotope Name Isotope Symbol # p+# n# e- Lithium 6Li 6 Lithium 7Li 7 Iron Fe 28 Iron Fe-31 Chlorine Mercury 3 3 26 17 80 3 4 18 120 3 3 26 17 80 54 57 Cl - 35 Hg - 200

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The Electron Cloud

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Atomic Structure electron cloud The region of the atom around the nucleus where the electrons are located Makes up most of the atoms size Mostly empty space Made up of energy levels that e - can move in and out of by absorbing & releasing energy e - absorb energy and move to higher levels or release energy and drop back to lower levels Nucleus 1 st Energy Level: holds up to 2 e - 2 nd Energy Level: holds up to 8 e - 3 rd Energy Level: holds up to 18 e - 4 th Energy Level: holds up to 32 e - Formula: ?? Skip valence e- for now

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Atomic Theory Electron Cloud Energy levels were proposed by Neils Bohr in 1913 His data supported that e - absorb heat/electrical energy & then release the energy as certain colors of light He concluded that e - orbited the nucleus in energy levels Jumped to higher levels when absorbing energy Released light energy when they fell back down https://www.youtube.com/watch?t=175&v=CUk 3enr-m0w https://www.youtube.com/watch?t=175&v=CUk 3enr-m0w

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Atomic Model Bohr Model Neils Bohrs model is sometimes called the planetary model but we usually call it the Bohr Model light released e.l. = 3 e.l. = 2 e.l. = 1 Time for a demo

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Electron Cloud Later Discoveries In 1926 Erwin Schrodinger & Max Born proposed that electrons actually behaved more like waves than particles and therefore proposed the wave model. Schrodinger is famous for his Schrodingers Cat example used to explain this model The quantum mechanical model of the electron cloud is our current model and many scientists have contributed to its development. discovered e - exist within orbitals, which are not circular, within the energy levelswhich are not circular dark, shaded areas of the cloud are more likely to contain e -