Unit 3. The Atom & Modern Atomic Theory

Unit 3 The Atom & Modern Atomic Theory

Theories of the Atom Early Models & Thoughts: Democritus Matter is made up of tiny particles called atoms. Smallest unit that retains the identity of the element

Theories of the Atom John Dalton: Hard Sphere model The main points of Dalton's atomic theory were: Elements are made of extremely small particles called atoms. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed. Atoms of different elements combine in simple wholenumber ratios to form chemical compounds. In chemical reactions, atoms are combined, separated, or rearranged.

Theories of the Atom J.J. Thomson: Cathode Ray Tube experiment. Found the atom to be a positively charged sphere, negatively charge electrons embedded within the sphere. Discovered the electron Plum pudding model of the atom.

Cathode Ray Tube Experiment http://www.youtube.com/watch?v=o9goyscbaz k

Gold Foil Experiment http://www.youtube.com/watch?v=5pzj0u_xm bc http://www.youtube.com/watch?v=xbqhkraf8ie &feature=related

Theories of the Atom Ernest Rutherford Gold Foil experiment : Shot alpha particles at gold foil. Some went straight through others bounced back & deflected at odd angles. His 3 conclusions: 1. Atoms are mostly empty space, 2. Dense positive center. 3. Most of the mass of the atom is in the center (nucleus) Model of the atom has a nucleus with orbiting electrons.

Theories of the Atom Bohr Model: Planetary Model of the atom The atom contained a nucleus w/ protons and Neutrons Each electron in an atom is allowed to be in certain orbits that correspond to different amounts of energy. Electrons can jump orbits (energy levels)

Theories of the Atom Electron Cloud/ Wave Mechanical Model: Current model Protons & neutrons in the nucleus Electrons are in areas called orbitals and the model is based on the probability of finding an electron. Greater cloud density = increased probability of finding an electron. There is a greater chance of finding an electron in certain orbitals.

Theories of the Atom The modern model of the atom is based on the work of many scientists over a long period of time.

Venus Explains the Atom https://www.youtube.com/watch?v=hhbqijz8w CM

Atomic Structure

Atomic Structure Moseley: Devised the concept of atomic number Said atomic number of an atom is equal to the number of protons in the atom's nucleus.

The Periodic Table can tell you about an atom. Atomic Mass = #Protons + #Neutrons # Protons

Atomic Structure 3 Important Ideas: 1 2 The atomic number is the ID of the element unique to each element). 3

Atomic Structure 3 Important Ideas: 1 2 The atomic number is the ID of the element unique to each element). In a neutral atom: # of Protons = # of electrons 3

Atomic Structure 3 Important Ideas: 1 2 The atomic number is the ID of the element unique to each element). In a neutral atom: # of Protons = # of electrons 3 When an atom gains or loses an electron, it is now an ion

Atomic Structure Charge = # of protons # of electrons

Atomic Structure Example 1. What is the name of the element whose atoms have 11 protons? Example 2: How many protons and electrons in an oxygen atom? Example 3: How many electrons and protons in Na +?

Atomic Structure Example 4: Write the symbol for the ion with 9 protons and 10 electrons. Example 5: Write the symbol for the ion with 13 protons and 10 electrons. Example 6: How many protons & electrons in S -2 ion?

Atomic Structure, Part II Reflect: Why use the a.m.u. scale to measure the mass of an atom?

Atomic Structure, Part II a.m.u. : Atomic Mass Unit To determine the number of neutrons: # of neutrons = mass number atomic number

Atomic Structure, Part II Example 1: How many neutrons, protons, and electrons are in an ion? Example 2: Determine the number of protons, electrons, and neutrons this ion:

Atomic Structure, Part II Example 3: Write the complete chemical symbol of an element with 21 protons, 24 neutrons, and 18 electrons. Example 4: Write the complete chemical symbol of an element with 53 protons, 74 neutrons, and 54 electrons.

Ar 18 18 Element Symbol Mass Number # of Protons # of Neutrons # of Electrons Ion Charge Boron 5 0 Na 11 +1 1 0 0 17 18 Al 13 +3 9 10 Oxygen O -2 Calcium 20 18 Sulfur 32 0

Element Symbol Mass Number # of Protons # of Neutrons # of Electrons Ion Charge Boron B 11 5 6 5 0 Na 11 +1 1 0 0 17 18 Al 13 +3 9 10 Oxygen O -2 Calcium 20 18 Sulfur 32 0 Ar 18 18

Element Symbol Mass Number # of Protons # of Neutrons # of Electrons Ion Charge Boron B 11 5 6 5 0 Sodium Na 23 11 12 10 +1 1 0 0 17 18 Al 13 +3 9 10 Oxygen O -2 Calcium 20 18 Sulfur 32 0 Ar 18 18

Element Symbol Mass Number # of Protons # of Neutrons # of Electrons Ion Charge Boron B 11 5 6 5 0 Sodium Na 23 11 12 10 +1 Hydrogen H 1 1 0 1 0 17 18 Al 13 +3 9 10 Oxygen O -2 Calcium 20 18 Sulfur 32 0 Ar 18 18

Element Symbol Mass Number # of Protons # of Neutrons # of Electrons Ion Charge Boron B 11 5 6 5 0 Sodium Na 23 11 12 10 +1 Hydrogen H 1 1 0 1 0 Chlorine Cl 35 17 18 18-1 Al 13 +3 9 10 Oxygen O -2 Calcium 20 18 Sulfur 32 0 Ar 18 18

Element Symbol Mass Number # of Protons # of Neutrons # of Electrons Ion Charge Boron B 11 5 6 5 0 Sodium Na 23 11 12 10 +1 Hydrogen H 1 1 0 1 0 Chlorine Cl 35 17 18 18-1 Aluminum Al 27 13 14 10 +3 Fluorine F 19 9 10 10-1 Oxygen O 16 8 8 10-2 Calcium Ca 40 20 20 18 +2 Sulfur S 32 16 16 16 0 Argon Ar 40 18 22 18 0

Atomic Structure, Part II Isotope: Same element (same # of protons), but different number of neutrons. (So the mass of each isotope is different). Remember: atomic mass is the weighted average of masses of these isotopes.

Atomic Structure, Part II (isotope mass)(% abundance) + (isotope #2 mass)(% abundance).. 100 Example 1: Chlorine has two isotopes, chlorine 35 and chlorine 37. Approximately 75% is Cl-35 and 25% is Cl-37. Which isotope should the weighted average be closer to?

Atomic Structure & Isotopes (isotope mass)(% abundance) + (isotope #2 mass)(% abundance).. 100 Example 2: Boron-10 has a relative abundance of 19.78%. Boron-11 has a relative abundance of 80.22%. Calculate the average atomic mass.

Atomic Structure & Isotopes (isotope mass)(% abundance) + (isotope #2 mass)(% abundance).. 100 Example 3: The relative masses and abundances of Iodine are given below. Calculate the average atomic mass. Isotope % Abundance I-127 80.0% I-126 17.0% I-128 3.0 %

Reviewing the Atom The Wave-Mechanical Model of the Atom

Reviewing the Atom Protons Neutrons Electrons Charge Mass Where found If you change the number of these particles, you get How to figure out how many an atom has

Bohr Model & Electron States

Bohr Model & Electron States Electron Configurations: Ordered sequence showing how many electrons are in each Principle Energy Level for a particular atom. Given in your reference table, starting from energy level 1 Note the * for elements 72 and up

Ex: 2-8-1 or 2-4 or 2-7 Bohr Model & Electron States Valence Electrons: Outer most electrons found in the last Principle Energy Level that are used for bonding. Hint: Look at your periodic table. In each box is the Bohr e- configuration. The last number are the valence electrons.

Bohr Model & Electron States

Bohr Model & Electron States Practice: Write the electron configurations of the following atom and then state how many principle energy levels each element has. Element Electron Configuration # of Principle Energy Levels Neon Strontium Bromine Magnesium Copper

Bohr Model & Electron States Directions: Draw a Bohr model of the following neutral atoms using the electron configuration on the Periodic Table. Include the number of protons and neutrons in the nucleus and write the electron configurations in the box below.

Bohr Model & Excited States

Ground State: Bohr Model & Electron States All electrons are in their lowest possible state. Ex: Magnesium Excited State: 2-8-2 2-7-3 An electron has jumped to a higher principle energy level. Ex: Magnesium

Bohr Model & Electron States

Electromagnetic Spectrum

In different scenarios, light behaves as a continuous wave AND as individual particles.

Light & Quantum Theory Much of the understanding of how electrons behave in atoms comes from studies of how light interacts with matter.

One photon interacts with 1 atom of matter at a time.

Depending on what orbital the electrons jumped to and fell from, there will be photons of different energy emitted. We can see the color of those photons.

Electron Transitions Key Idea #1 Longer wavelengths (red end of spectrum) have less energy. Shorter wavelengths (violet end of spectrum) have more energy

Electron Transitions Key Idea #2 When electrons move up energy levels, this requires energy (remember protons and electrons attract!). (Ground Excited) When electrons move down energy levels (Excited Ground), they emit energy as light waves Different transitions result in different energy emissions (i.e. different colors)

Electron Transitions Key Idea #3 Each atom emits a specific number and pattern of bands based on its electron configuration when you pass its light through a prisim.

Bohr Model & Electron States Ground State: When electrons are at their lowest possible energy state. Example electron configuration: 2 8 1 Excited State: When an electron gains energy (heat or electricity) and jumps to a higher PEL. Example electron configuration: 2 7 3

Bohr Model & Electron States How Light is Produced: 1. Electron(s) absorb energy in the form of heat or electricity 2. Electron(s) then jump up to a higher PEL & are in the excited state. 3. The electron(s) then fall back down to the ground state. 4. When the electron(s) falls back to the ground state it emits a photon of light (energy absorbed = energy emitted).

Bohr Model & Electron States Flame Test: Metallic salts are put in a flame A specific color of light is given off

Bohr Model & Electron States Bright Line Spectrum: Electricity is run through a gas tube A specific color of light is given off Light is passed through a prism A unique patter of colored lines are produced Ca be used to ID an element!

Red light has the least energy. Violet light has the greatest energy.

Review of Light & Quantum Theory Much of the understanding of how electrons behave in atoms comes from studies of how light interacts with matter.

In different scenarios, light behaves as a continuous wave AND as individual particles.

One photon interacts with 1 atom of matter at a time. Energy, wavelength, frequency are associated with each photon.

Bohr took his model of the atom and stated that electrons can absorb certain amounts of energy and then release that energy in the form of a photon.

Review of Light & Quantum Theory When all electrons are at their lowest possible energy, it is called the Ground State. When the electron absorbs a specific amount of energy, it moves to a higher orbital and is in the excited state.

Depending on what orbital the electrons jumped to and fell from, there will be photons of different energy emitted. We can see the color of those photons.

Every atom has a range of colors emitted when their electrons get excited and fall back down. Sodium: Orange Copper: Green Strontium: Drk. Orange Mercury: Blue

The colorful lights of fireworks are emitted by "excited" atoms; that is, by atoms that have absorbed extra energy. Different compounds within the fireworks give them their signature colors.

Light can be further analyzed by passing it through a prism. White light when passed through a prism breaks up into all the colors of the rainbow (ROYGBIV)

When the color of light emitted by an atom is passed through a prism, only certain colors are observed. These specific colors are called a Bright Line Spectrum. Each line spectra is different for every element and can serve to identify a particular element. Hydrogen:

Electron Configurations Reflect: Think of electrons, all negatively charged, in a cloud around the nucleus. How can they be organized to minimize repulsion?

Electron Configuration3 Wave Mechanical Model: Electrons are organized in orbitals, or areas of probable electron location

Electron Configurations Heisenberg Uncertainty Principle: We cannot know both the direction and location of electrons measuring one changes the other

Organized by: which is like Principle Energy levels (7 total, numbered 1, 2, etc) Floors in an apartment Sublevels (Named s, p, d, f) The actual apartment Orbitals (Can hold only 2 electrons) Rooms in the apartment

S 1 Orbital Holds 2 e- P 3 Orbitals Holds 6 e- d 5 Orbitals Holds 10 e-

Each sublevel holds a different number of orbitals: s = 1 orbital = 2 electrons p = 3 orbitals = 6 electrons d = 5 orbitals = 10 electrons f = 7 orbitals = 14 electrons

Electron Configurations Principal Energy Level Type of Sublevel (shape of orbitals) Number of Orbitals in Sublevel Electron Capacity of Sublevel

Electron Configurations

Electron Configurations Sublevel: Sublevels are contained within a PEL. There are 4 shapes /types that are labeled with letters (s, p,d, f). *sublevels are regions of space where the electrons w/ specific energies live. s sublevel

Electron Configurations p sublevel

Electron Configurations d sublevel

Electron Configurations f sublevel

Electron Configurations Orbital: Orbitals make up the sublevels. Each orbital can hold only 2 electrons max. The p sublevel contains 3 orbitals. Each holds 2 electrons for a total of 6 electrons in the p sublevel s sublevel has 1 orbital. 2 e- max d sublevel has 5 orbitals. 10 e- max f sublevel has 7 orbital2. 14 e- max

Electron Configurations When writing an electron configuration, the general format is to list the information in the following order: PEL then sublevel then # of Electrons 1,2,3 s,p,d,f write as an exponent You start with the innermost electrons and continue describing the location of all electrons as you move away from the nucleus. General Trend: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2

Analogy Electron Apartment Complex: Each floor represents a PEL. On the first floor (n =1)there is only 1 apartment. Apartment s. It is the cheapest apartment (lowest in energy). It is a studio (one room) and can only hold 2 occupants (electrons). s n = 1

Analogy Electron Apartment Complex: On the second floor (n = 2)there are 2 apartments. One studio apartment (s) that can hold 2 people (which costs more since it is on the 2 nd floor) and a p apartment that has 3 bedrooms (2 people to a room) for a total of 6 occupants, which costs more than the studio because it is bigger. (*cost = energy) s p p p n = 2 s

Analogy Electron Apartment Complex: On the 3 rd floor (n = 3)there are 3 apartments. One studio apartment (s) that can hold 2 people (which costs more since it is on the 3 nd floor) and a p apartment that has 3 bedrooms (2 people to a room) for a total of 6 occupants, which costs more than the studio because it is bigger. Then there is the d apartment that has 5 bedrooms, 2 people to a room for a total of 10 occupants. s p p p d d d d d n = 3 s p p p s

Analogy Electron Apartment Complex: On the 4 th floor (n = 4) there are a total of 4 apartments. 1 studio, 1 three bedroom, a 5 bedroom and lastly the Penthouse with a total of 7 bedrooms (2 occupants to a room) that can house up to 14 people. This apartment costs the most to occupy. (The s, p and d apartments are also more expensive than the ones on lower floors). n = 4 s p p p d d d d d f f f f f f f s p p p d d d d d s p p p s

Analogy

Be: Practice C: F: Ne+: * Exponents should add up to the total # of electrons in the atom!

Agenda Warm up Complete the top Reviewing the Atom In your work packet you got last week Notes on Orbital notation Practice notation H.W. 3.7

Orbital shapes

Using the Periodic Table to Write Sublevel Electron Configurations

Practice Examples H: He: Li: Be: B: C: N:

Orbital Notation Electron Configurations: 1s 2 Orbital Diagrams:

Orbital Notation Orbital Diagram: A pictorial representation (using arrows to represent electrons) of sublevel electron configurations. Examples of Orbital Diagrams: Orbital diagram for Oxygen

Orbital Notation Rules for Electron Configurations & Orbital Diagrams: Aufbau: Electrons are added 1 at a time to the lowest energy orbitals available until all the electrons are used.

Orbital Notation Rules for Electron Configurations & Orbital Diagrams: Pauli Exclusion Principle: An orbital can only hold a maximum of two electrons.

Orbital Notation Rules for Electron Configurations & Orbital Diagrams: Hund s Rule: Electrons of the same energy spread out before pairing up.

Orbital Notation Rules for Electron Configurations & Orbital Diagrams: Example: Orbital Diagram for Fluorine 9 electrons 1s 2 2s 2 2p 5

Sodium: Practice

Sodium +1 ion: Practice

Chlorine: Practice

Atomic Structure Protons Neutrons Electrons Found in the nucleus (+) charge Mass of 1 amu # of protons = Atomic # # of protons = # of electrons in a NEUTRAL atom # of protons = the nuclear charge.

Atomic Structure Protons Neutrons Electrons Found in the nucleus (+) charge Mass of 1 amu # of protons = Atomic # # of protons = # of electrons in a NEUTRAL atom # of protons = the nuclear charge. Found in the nucleus (0) charge neutral mass of 1 amu Found in orbitals ( e- clouds) surrounding nucleus ( - ) charge Mass 1/1836th of a proton # of e- = # of protons in a NEUTRAL atom