Atoms: The Building Blocks of Matter Unit 2

 Introduction to the Atom Modern Atomic Theory Subatomic Particles Isotopes Ions Essential Standards and objectives: Analyze the structure of atoms, isotopes, and ions Analyze an atom in terms of the location of electrons Explain the emission of electromagnetic radiation in spectral form in terms of the Bohr model Explain the process of radioactive decay using nuclear equations and half-life Analyze quantitatively the composition of a substance. (Introduction to moles)

Organization of the Periodic Table Columns – Groups All the elements have similar chemical and physical properties All will chemically react in a similar way Names of groups Rows – Periods Elements have same number of energy levels

Video Break  Crash Course The Periodic Table  Diomg&index=4&list=PL8dPuuaLjXtPHzzY uWy6fYEaX9mQQ8oGr

The Atom: Smallest particle of an element that retains the chemical properties of the element. Essential Questions: What is an atom? What is its structure? What determines properties of an element?

Atoms act in orderly, predictable ways.

Modern Atomic Theory 1. All matter: 2. Atoms of a given element: 3. Atoms cannot be created nor destroyed in: 4. In chemical reactions, atoms are

Atomic Theory (cont.) 5. To form compounds: 2 or more elements bond

Atomic Mass Unit AMU The “amu” is defined as one twelfth of the mass of an atom of carbon-12 (with 6 protons and 6 neutrons) and has a value of ×10 −27 kg.carbon-12kg AMU = relative measurement and used for comparison

Summary Table: Atomic Structure- Subatomic Particles Subatomic LocationCharge Mass Importance Particle AMU

Designation of Atomic Structure  Atomic number (Z): On the Periodic Table:  Mass number (A): On the Periodic Table:

Representing atoms  Information from symbols and the Periodic Table

What does this symbol tell us? Protons: Neutrons: Electrons:

Designations for the Atomic Structure Atomic number (Z): - On the Symbol - On the Periodic Table Mass number (A): - On the Symbol - On the Periodic Table 20 Ca 40.08

Review: What is Z? What is A? Determine the number of protons, neutrons, and electrons. 31 Ga Gallium Ge Germanium 72.61

Periodic Table 16 S S How can we tell which is the atomic number and the mass number?

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Isotopes

Isotopes:  Atoms of an element with different masses Naturally occurring Some are stable and some are radioactive (unstable)  Isotopes of an element have the same number of ___________ and a different number of ______________.

Identifying Isotopes  Isotope Notation On the Periodic Table, the number with the Decimal point is:

Atomic Mass  Weighted Average Mass of isotopes  Based on the percentage of each isotope present.

Grades are often computed using a weighted average.  Suppose that homework counts 10%, quizzes 20%, Labs 10% and tests 60%.  If: homework grade is 92 quiz grade is 68 lab grade is 88 test grade is 81 What’s the overall grade?

Practice  Atomic Structure Identify the number of proton, neutron, & electrons of an atom of a specific element Rounding the atomic mass on the Periodic Table gives the mass of the most common isotope  Atomic Number & Isotopes Correct symbol: A & Z Complete the table Complete the questions.

Find Average Atomic Mass

Atomic Number & Isotope

Isotopes: Atomic Number & Mass Number ElementIsotope Symbol Atomic Number Z Mass Number A # of protons # of neutrons # of electrons

Stable Isotopes - frequency  pertable/PTFRAME.HTM pertable/PTFRAME.HTM

Development of the Modern Atomic Model Here are several models of the atom as they were developed in history:

Bohr Diagram What does it represent? How many electrons can be held in each ring? What does the outer shell represent?

Representing atoms with the Bohr model

Representing atoms with the Bohr Model

Bohr Model – Simplified but Useful Model Group 1 Group 2 Groups 2-12 Group 13 Group 14 Group 15 Group 16 Group 17 Group 18 P1 P2 P3

Bohr Model & the Periodic Table Making Conclusions Compare and Contrast Why are elements placed in a group (column)? Why are elements placed in a period (row?)

Changing An Atom Changing an Atom

Ions  Atoms can lose or gain electrons when bonding to make ionic compounds  We keep track of the number of electrons that can be lost or gained with oxidation numbers (also known as charges)  Ions are charged particles –when an atom has too many or too few electrons to be neutral No change to the nucleus Proton and neutrons stay the same number.

Ions – Charged Particles 7. When atoms of elements form ions (cations or anions) they must either __________ or _______ valence electrons. Gain/lose? Charge Ion type? Metals Non-metals

Representing atoms with the Bohr Model

Why are ions important?  The ___________________ charged particles are like a magnet.

Ions Lithium atom - Lithium ion Ion Symbolp+nºe- Fluorine atom Fluorine ionp+nºe-

Ions and Charge Net electric charge Note change 8

Ions and Charges for Representative Elements (Oxidation number keep track of electrons) Group 1 Group 2 Group 13 Group 14 Group 15 Group 16 Group 17 Group 18

Nuclear Chemistry

Types of Radiation

Alpha Decay

Beta decay

Gamma Decay

Radiation Strength

Nuclear Equations H Be ---> 6 3 Li + ? Al He ---> P + ? Mg  Mg + ? U  Th + ? C  0 -1 e + ? Pu He  Cm + ? Nuclear Equations Practice Website

Half-life  Measure of Radioactive decay rate.  Measured as the time it takes for ½ of a sample of radioisotope’s nuclei to decay into its products.

Half Life Decay of a radioisotope Number of Half-Lives Elapsed timeAmount remaining g 11.5 year50 g 23 years25 g years12.5 g

Half Life Problems  How much of a 100g sample of an unstable isotope remains after 25 years if the half life is 5 years? 3.1 g

Half Life Problems  How much of a 60g sample of an unstable isotope remains after 2 days if the half life is 12 hours? 7.5 g

Half Life Problems  How much of a 20 g sample of an unstable isotope remains after 6 sec if the half life is 0.5? g

Atomic Nucleus (also known as nuclide)  Mass  Energy  Volume

Radioactive Isotopes A radioactive isotope has an unstable nucleus that undergoes spontaneous changes. - Emits particles and energy - Transmutates into another element

Particles emitted from a radioactive isotope Type Symbol Charge Mass

Nuclear reactions Total number of atomic numbers and the total mass numbers must be equal on both sides of the equation. Examples:

Radioactive decay No 2 radioactive isotopes decay at the same rate. Therefore, decay rate can be used to identify the isotope. Decay is measured by half life.

Fission and Fusion

Origins of Element

Got Calcium  Where are most elements created?  When was H and He created?  What elements are made by small stars?  What additional elements are made by large stars?  What elements are made by supernovae (large exploding stars)?