Essential Question: What type of model did Thompson, Rutherford, and Bohr propose about the atom. ATOMIC STRUCTURE Atom- smallest particle of an element that retains its identity in a chemical reaction History of the atom: Greeks thought matter is composed of fire, water, and wind.

Democritus (460 BCE- 370 BCE) Suggested existence of atoms Said atoms were indivisible earth and indestructible

Essential Question: What is John Dalton’s atomic theory? Dalton (1808)  Used experimental methods to transfer Democritus’s ideas into scientific theory

Atomic Theory Elements are composed of indivisible atoms Elements are composed of indivisible atoms All atoms of a given element are identical All atoms of a given element are identical Atoms of different elements are different therefore have different masses Atoms of different elements are different therefore have different masses Compounds are formed by a combination of different elements, Compounds are formed by a combination of different elements,

J.J Thomson (1897) Discovered electrons by passing an electric current through gas at a low temperature Named the negatively charged particles electrons An atom was a positively charged, jelly-like, with negatively charged electrons scattered throughout. Ex: Raisins in plum pudding model

Rutherford’s Experiment

Ernest Rutherford (1911) Tested “plum pudding theory” by using alpha particles (positive charged particles smaller than an atom) Tested “plum pudding theory” by using alpha particles (positive charged particles smaller than an atom) Directed alpha particles at a thin sheet of gold foil Directed alpha particles at a thin sheet of gold foil Alpha particles should have passed through the sheet, but instead most passed through, but some were greatly deflected and some bounced back. Alpha particles should have passed through the sheet, but instead most passed through, but some were greatly deflected and some bounced back. Concluded that atoms have a dense central core, nucleus, while the remainder is mainly empty space Concluded that atoms have a dense central core, nucleus, while the remainder is mainly empty space Developed the concept of a nucleus (protons and neutrons) found in the nucleus and electrons are around the nucleus Developed the concept of a nucleus (protons and neutrons) found in the nucleus and electrons are around the nucleus Could not explain chemical properties of elements Could not explain chemical properties of elements

Bohr’s Model

Neil Bohr (1913) Proposed the planetary model Proposed the planetary model Said that electrons are found in specific circular pathways (energy levels or orbits) around the nucleusSaid that electrons are found in specific circular pathways (energy levels or orbits) around the nucleus Every possible orbit has a fixed amount of electronsEvery possible orbit has a fixed amount of electrons Lowest energy is found in the energy level closest to the nucleusLowest energy is found in the energy level closest to the nucleus Electrons can jump from electrons level to electron level therefore electrons must gain/loose energy as travel from energy level to energy levelElectrons can jump from electrons level to electron level therefore electrons must gain/loose energy as travel from energy level to energy level

Comparison of Models:

Quantum of Energy: Amount of energy (photon) required to move an electron from 1 energy level to another energy level. Energy levels are closer together in higher energy levels, therefore requires energy to go from different energy levels (Less energy higher up)

Essential Questions: What is the quantum wave mechanical model of an atom? What are orbitals? Quantum Mechanical Model (Wave- Mechanical Model) Proposed by Erwin Schrödinger (1926) Said levels (shells) have distinct amounts of electrons moving in areas called orbital

Orbital: Region in which there is a high probability of finding an electron (based on the electron posses by the electrons.) Looks like a cloud around the nucleus

Essential Questions: What is the structure of an atom? What is the atomic number and mass number? Structure of the atoms: Atoms are composed of protons, neutrons and electrons Atoms are composed of protons, neutrons and electronsNeutron: Found in nucleus Found in nucleus No charge No charge Mass= 1 amu Mass= 1 amu Symbol 1 0 n Symbol 1 0 n

Atomic mass unit (amu) – 1/12 the mass of Carbon-12 atom Proton: Found in nucleus Found in nucleus + charge + charge Symbol 1 1 P or 1 1 1H Symbol 1 1 P or 1 1 1H Mass = 1 amu Mass = 1 amu  Number of protons = the number of electrons

Atomic Number  Number of protons in an atom  Periodic Table is arranged according to increasing atomic number

► Electrons  Found in orbital outside nucleus  Negative charge  Mass of 1/1836 amu  Symbol 0 -1 e  Number of electrons = number of protons ► Ex.: Na- atomic # is 11, therefore 11 protons and 11 electrons ► **All atoms are neutral, because the number of protons equals the number of electrons***

Mass number- sum of the protons and neutrons in an atom Ex: Cl 17 protons + 18 neutrons = 35 is the mass number Mg12 protons + 12 neutrons = 24 mass number

Essential Question: What is an isotope? Isotopes Atoms of the same element with different number of neutrons Atoms of the same element with different number of neutrons Therefore have a different mass Therefore have a different mass Chemically alike because they have same number of electrons and protons which are responsible for chemical behavior Chemically alike because they have same number of electrons and protons which are responsible for chemical behavior Ex.: C-14  8 neutrons Ex.: C-14  8 neutrons 14 6 C 14 6 C C-12  6 neutrons C-12  6 neutrons 12 6 C 12 6 C

Essential Questions: What is atomic mass? What is mass number? Atomic Mass: ► Average mass of atoms in a naturally occurring sample of an element. ► Reflects both mass and relative abundance of isotopes as they occur in nature.

Atomic Problems: Atomic Problems: What is the most abundant isotopes of element oxygen( atoms mass = amu) What is the most abundant isotopes of element oxygen( atoms mass = amu) O-16 because is closet to 16 O-16 because is closet to 16 What is the most abundant isotope of the element gold? (atomic mass = amu) What is the most abundant isotope of the element gold? (atomic mass = amu) Au-197 Au-197

An element consists of two isotopes. Isotope A has an abundance of 75.00% and its mass is amu. Isotope B has an abundance of 25.00% and its mass is amu. What is the atomic mass of the element? Isotope AIsotope B 25% 75% amu amu Convert % into decimals Atomic mass = ( amu x.7500) + ( amu x.2500) = amu

Carbon has two naturally occurring stable isotopes. Most carbon atoms % is C-12, while the remaining 1.108% is C- 13. What is the atomic mass of carbon? KnownUnknown KnownUnknown 98.89% C-12atomic mass = amu 1.108% C-13 12amu x = amu 13 amu x = amu 11.87amu amu =12.01 amu

Essential Question: What is an ion? Ion: An atom that has lost or gained electrons. Positive ion – lost electrons. Ex: B +3 lost 3 electrons Negative ion –gained electrons Ex: Cl -1 Refer to periodic table

Oxidation states- number of electrons lost or gained by an atom to become an ion. Some elements have multiple oxidation states, depending on what substance they bond to. Some elements have multiple oxidation states, depending on what substance they bond to. Ex: S -2,+4,+6  Loose or gain electrons to become stable.

How many electrons, protons, and neutrons are in the following ions? F -1 N -3 Na +1 Cl +5 Mg +2

There are 7 energy levels (shells). They are numbered 1-7. Energy level 1 is closest to the nucleus with the least amount of energy. Each successive energy level is further away from the nucleus, but has progressively more energy.

The energy level (shell) corresponds to the row (period) number in the periodic table.

Essential Questions: What are energy levels? How many electrons does each level contain? What are valence electrons? Each energy level (shell) can contain a maximum number of electrons. 1 st level- 2 electrons 2 nd level-8 electrons 3 rd level-18 electrons 4 th level -32 electrons

Essential Question: What is electron configuration? Electron configuration-arrangement of electrons by energy level (shell). Exs.” Mg st level-2 electrons 2 nd level-8 electrons 3 rd level-2 electrons What is the configuration of krypton? Kr st level –2 electrons 2 nd level-8 electrons 3 rd level-18 electrons 4 th level-8 electrons

Valence Electrons- electrons in the outermost energy level. Ex: Be 2-2 Cl Corresponds to group number in the periodic table. Group 2 elements have 2 valence electrons: Be 2-2 Mg Ca Ba

Valence electrons are those that are involved in a bond. Valence electrons are those that are involved in a bond. Valence electrons are those that an atom gains or loses to become an ion. Valence electrons are those that an atom gains or loses to become an ion. Ex: Na Na +1 F 2-7 F

Essential Questions? What is the ground state? What is the excited state ? What is quanta? Ground state: Electrons occupy the lowest energy levels. Electrons occupy the lowest energy levels. Given on the periodic table. Given on the periodic table. Ex: C 2-6 N 2-5 N 2-5

Excited State: When an electron temporarily moves to a higher energy level. When an electron temporarily moves to a higher energy level. Electrons absorb energy when they move to a higher energy level. Electrons absorb energy when they move to a higher energy level. Exs.: C 2-4 ground state excited state excited state Cl ground state excited state excited state B 2-3 ground state 1-4 excited state 1-4 excited state Electrons are arranged different from what is on the periodic tables Electrons are arranged different from what is on the periodic tables

Quanta Amount of energy absorbed by an electron moving to a higher energy level Often see its a color Atom is unstable Electrons will go back to its original level, therefore releasing the energy (quanta)

Spectrum: Pattern of light produced by an atom Distinctive for each element ( like a finger print)