The Structure of the Atom and the Periodic Table Chapters 4 and 5

Atomic Theories- Ancient Ancient times identify 4 elements: Fire Water Wind Earth They thought that these elements could be converted into each other through a cycle end

Atomic Theories- Ancient Democritus 1 st to propose that there is a smallest particle Matter was made up of atomos Atoms cannot be created, destroyed, or divided Aristotle Opposed Democritus’ view Did not agree with the concept of empty space Destroyed Democritus’ theory end

Atomic Theories- Modern John Dalton English Quaker Schoolteacher Father of modern atomic theory Spent a great deal of time studying the behavior of gases He noticed that in every sample the ratio of the elements was always the same end

Atomic Theories- Modern Dalton's Atomic Theory: All elements are made of atoms Atoms of the same element have the same mass This was later proved wrong- Isotopes Atoms of different elements have different masses Atoms combine in whole number ratios You can't have half of an atom in a compound Dalton's Atoms Dalton went back to Democritus' view. All matter is made up of individual particles called atoms, which cannot be divided Atoms are little spheres Like marbles end

Atomic Theories- Modern Atom The smallest particle of an element that retains the properties of the element end

Atomic Theories- Modern J. J. Thomson Performed cathode ray tube experiments Discovered the electron Proved that atoms can be broken up Dalton was wrong Created the Plum Pudding Model When electricity moves through a gas it produces a glowing beam (neon signs) When a magnetic field was applied the beam went toward the positive plate end

Atomic Theories- Modern Thomson had to come up with a new model to explain the electrons The Plum Pudding Model Large area of positive charge Small packets of negative charge Think: Chocolate Chip Cookies end

Atomic Theories- Modern Ernest Rutherford Conducted the Gold Foil Experiment Shot particles at thin pieces of gold foil Expected to see particles pass straight through Some particles bounced almost straight back end

Atomic Theories- Modern His experiment showed that the Plum Pudding Model was wrong Rutherford came up with a new model of an atom A small, dense, positive nucleus Electrons are outside the nucleus Atoms are mostly empty space + Nucleus Electrons are somewhere in this area end

Structure of the Atom Protons, electrons, and neutrons are subatomic particles They make-up an atom You must be able to identify them by mass, charge, and location end

Structure of the Atom The Nucleus Small dense region in the center of an atom Contains all of an atom’s positive charge And almost all of its mass. Contains protons and neutrons end

Structure of the Atom Proton (p + ) Found inside the nucleus Charge of +1 Same mass as a neutron If you change the # of protons you get a different element end

Structure of the Atom Electron (e - ) Charge of -1 Found outside the nucleus Almost no mass compared to the proton If you change the # of electrons you get a ion end

Structure of the Atom Neutron (n 0 ) No charge Same mass as a proton Found in the nucleus with the proton If you change the # of neutrons you get different isotopes end

Review ParticleSymbolLocationRelative Mass Relative Electrical Charge Change in Number Electrone-e- Outside the Nucleus 1/1840 Basically = 0 Ions Protonp+p+ Nucleus1+1Elements Neutronn0n0 Nucleus10Isotopes end

Isotopes Atoms of the same element Have different numbers of neutrons Which means different mass numbers All elements have isotopes In nature the elements occur as a mixture of isotopes end

Structure of the Atom Mass Number The relative mass of each atom The number of protons + the number of neutrons Different isotopes have different mass numbers Changes the # of neutrons! Mass# = (Atomic#) + (# of neutrons) end

Structure of the Atom Atomic Number The number of protons in the element This defines each element Equals the number of electrons in a neutral atom Atomic Number end

Structure of the Atom Atomic Symbols – 1 or 2 letters – The 1 st letter is always capitalized the 2 nd is always lowercase Make sure to write your letters correctly!!!!! – The element’s name is just below the symbol Atomic Symbol Element’s Name end

Structure of the Atom Atomic Mass – Weighted average mass for all isotopes of each element – NOT the same as the Mass Number Atomic Mass end

Structure of the Atom Writing Atomic Symbols – Since every element has isotopes scientists have write symbols so the know which one they are talking about – There are 3 ways to write the symbols: Carbon- 12 C- 12 Name and Mass Number Symbol and Mass Number Symbol Mass Number Atomic Number end

Structure of the Atom NameSymbolProtons Neutron s Electron s Atomic Numbe r Mass Number Carbon C end

Atomic Theories- Modern Rutherford's model was good, but it didn't talk about the electrons Bohr Model (Solar System Model) Took Rutherford's model and put electrons into energy levels Electrons change energy levels when they either gain or lose energy Electrons cannot be between levels Electrons can move more than 1 level at a time end

Atomic Theories- Modern In the Bohr Model: – Protons and Neutrons form a nucleus – Electrons are placed in rings around the nucleus Each energy level can only hold a certain number of electrons Energy Level# of electrons end

Atomic Theories- Modern Lets draw H-1 p = 1 n = 0 e = 1 Lets draw He-4 p = 2 n = 2 e = 2 Lets draw Li-6 p = 3 n = 3 e = 3 Lets draw Na-22 p = 11 n = 11 e = 11 end

Atomic Theories- Modern Electrons want to be in the lowest energy level possible Ground state All electrons are in the lowest possible energy levels The most stable Excited state At least 1 electron is not in the lowest possible energy level end

Atomic Theories- Modern Bohr's model was good, but it had problems We can never be sure of exactly where electrons are located Electron Cloud Model With some fancy math, we figured out an area around the nucleus where the electrons are going to be 95% of the time This area is known as an Orbital Each orbital can only hold 2 electrons end

The Periodic Table By 1860 scientists had discovered 63 elements But there was no good way to organize them Scientists just had to memorized everything about every element This changed when Mendeleev created a way to classify the elements end

The Periodic Table Mendeleev’s Periodic Table: Elements with similar properties were placed in the same column The mass of the elements increased along each row end

The Periodic Table Mendeleev left several blank spaces in his periodic table These spaces were for elements that had not been discovered yet Mendeleev predicted what properties these elements would have based on the elements around them end

The Periodic Table The Modern Periodic Table: Based on Mendeleev’s table Elements with similar properties are in the same column Columns are called Groups Numbered 1 to 18 (from left to right) Atomic Numbers (# of protons) increase going across the table Rows are called Periods Numbered 1 to 7 (from top to bottom) end

The Periodic Table This is the full Periodic Table As you can see it is REALLY long Way too long to fit on a page end

The Periodic Table In order to make everything fit on 1 page, we take out the Lanthanides and Actinides. They are moved to the bottom of the table end

The Periodic Table Metals Left of the stair-step line Francium (Fr) is the most reactive Moving away from Fr, metals become less reactive Good conductors of electricity and heat Mostly solids at room temperature High melting and boiling points Malleable and ductile end

The Periodic Table Nonmetals Right of the stair-step line Fluorine (F) is the most reactive nonmetal Moving away from F, nonmetals become less reactive Poor conductors of heat and electricity Mostly gases at room temperature Low melting and boiling points Not malleable and not ductile end

The Periodic Table Metalloids Touching the stair-step line Have properties that fall between those of metals and nonmetals This depends on the temperature end

The Periodic Table Alkali Metals Group 1 EXTREMELY REACTIVE! Alkaline Earth Metals Group 2 end

The Periodic Table Transition Metals – Groups 3 to 12 – Have a wide variety of properties Lanthanide and Actinide Series – At the bottom of the table – All are radioactive end

The Periodic Table Halogens Group 17 Highly Reactive Noble Gases Group 18 Extremely Unreactive THEY DO NOTHING! end

The Periodic Table Atomic Size – Francium (Fr) is the largest atom – Helium (He) is the smallest atom – The closer to Fr, the larger the atom Valence Electrons – Electrons in the highest energy level – These give elements their chemical properties Group: # of Valence: end