Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–1 Welcome ! Review: What is matter, and why does matter matter? Today: Atomic structure and the periodic table.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–2 Atomic Theory of Matter Dalton’s Atomic Theory –All matter is composed of indivisible atoms. An atom is an extremely small particle of matter that retains its identity during chemical reactions. –An element is a type of matter composed of only one kind of atom, each atom of a given element having the same properties. Mass is one such property. Thus the atoms of a given element have a characteristic mass.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–3 1.A compound is a type of matter composed of atoms of two or more elements chemically combined in fixed proportions. 2.The relative numbers of any two kinds of atoms in a compound occur in simple ratios. 3.Water, for example, consists of hydrogen and oxygen in a 2 to 1 ratio. 4.A chemical reaction consists of the rearrangements of the atoms present in the reacting substances to give new chemical combinations present in the substances formed by the reaction. 5.Atoms are not created, destroyed, or broken into smaller particles by any chemical reaction. Atomic Theory of Matter Postulates of Dalton’s Atomic Theory

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–4 Atomic Theory of Matter The nuclear model of the atom. Ernest Rutherford, a British physicist, put forth the idea of the nuclear model of the atom in 1911, based on experiments done in his laboratory by Hans Geiger and Ernest Marsden.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–5 A. Develop new groups. The groups should contain folks from different areas and grade levels. (No one in the same group should have the same colored dot) B. With your new group, answer the following questions:

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–6 1. Most of the mass of the atom is concentrated in a very small, dense central area, later called the nucleus, which is about 1/100,000 the diameter of the atom. This was proposed as a result of what data? 2. The rest of the atom is apparently “empty space”. This was proposed as a result of what data? 3. The central, dense core of the atom is positively charged, with the nuclear charge equal to about one-half the atomic mass. This was proposed as a result of what data Questions for Discussion:

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–7 Atomic Target Practice: Pre-lab questions 1. This activity is a simulation of Rutherford’s scattering experiment. Read the entire procedure and compare the components used in this simulation to Rutherford’s original experiment. Discuss what each component in our simulation corresponds to in the original experiment. 2. The key skills in this activity, as in Rutherford’s experiment, are the ability to make careful observation and to draw reasonable hypotheses. Assume that the marble strikes following sides of a possible target. Sketch the path the marble might be expected to take in each case. 3. Discuss what information can be inferred if the marble rolls straight through without striking the unknown target.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–8 1. Marbles correspond to alpha particles Board corresponds to the gold foil target Unseen object corresponds to the atomic nucleus Traced path of the marble corresponds to the scattering angles of the alpha particles Knowing where the marble rolls in one side and out the other is an important first step for determining the size of the object and its position on the board. Atomic Target Practice: Pre-lab questions

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–9 Atomic Target Practice: Post-lab questions 1. Draw the general size and shape of the target to approximate scale in the square 2. The speed of the marble rolls was a uncontrolled variable in this activity. How would the outcome of the scattering test have been different if the marble speed had been faster or slower? 3. Compare the overall size of the target with the size of the marble used to probe its structure. How would the outcome of the scattering test have been different if different size marbles had been used? Explain.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–10 Atomic Target Practice: Sample Data

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–11 Atomic Target Practice: Post-lab questions

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–12 –These experiments showed that the atom consists of two kinds of particles: a nucleus, the atom’s central core, which is positively charged and contains most of the atom’s mass, and one or more electrons. Atomic Theory of Matter The structure of the atom –Electrons are very light, negatively charged particles that exist in the region around the atom’s positively charged nucleus.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–13 Atomic Theory of Matter How many protons, neutrons and electrons in each of the following: protons neutrons electrons 23 Na 14 N 38 Ar 35 Cl 36 Cl Fe Protons Neutrons Electrons

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–14 –Since Dalton could not weigh individual atoms, he devised experiments to measure their masses relative to the hydrogen atom. Atomic Weights Dalton’s Relative Atomic Masses –Hydrogen was chosen as it was believed to be the lightest element. Daltons assigned hydrogen a mass of 1. –For example, he found that carbon weighed 12 times more than hydrogen. He therefore assigned carbon a mass of 12.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–15 –Dalton’s atomic weight scale was eventually replaced in 1961, by the present carbon–12 mass scale. Atomic Weights Dalton’s Relative Atomic Masses –One atomic mass unit (amu) is, therefore, a mass unit equal to exactly 1/12 the mass of a carbon–12 atom. –On this modern scale, the atomic weight of an element is the average atomic mass for the naturally occurring element, expressed in atomic mass units.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–16 The Periodic Table In 1869, Dmitri Mendeleev discovered that if the known elements were arranged in order of atomic number, they could be placed in horizontal rows such that the elements in the vertical columns had similar properties. A tabular arrangement of elements in rows and columns, highlighting the regular repetition of properties of the elements, is called a periodic table.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–17 Figure 2.15: A modern form of the periodic table.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–18 –A period consists of the elements in one horizontal role of the periodic table. The Periodic Table Periods and Groups –A group consists of the elements in any one column of the periodic table. –The groups are usually numbered. –The eight “A” groups are called main group (or representative) elements.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–19 –The “B” groups are called transition elements. The Periodic Table Periods and Groups –The two rows of elements at the bottom of the table are called inner transition elements. –Elements in any one group have similar properties.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–20 The Periodic Table Periods and Groups

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–21 The Periodic Table

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–22 The Periodic Table – web resources 1. Different periodic tables of Mendeleev - article 2.Mark Winter’s Web Elements 3. Interactive periodic table 4.ChemED DL – Periodic Table Live!

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–23 Discussion What questions did your group have prior to the activity? What challenges did you experience while completing the activity? Were your questions answered? If not, what adjustments could be made to the activity to help it better address your questions?

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–24 Chemical Formulas; Molecular and Ionic Substances The chemical formula of a substance is a notation using atomic symbols with subscripts to convey the relative proportions of atoms of the different elements in a substance. –Consider the formula of aluminum oxide, Al 2 O 3. This formula implies that the compound is composed of aluminum atoms and oxygen atoms in the ratio 2:3.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–25 –A molecule is a definite group of atoms that are chemically bonded together – that is, tightly connected by attractive forces. Chemical Formulas; Molecular and Ionic Substances Molecular substances –A molecular substance is a substance that is composed of molecules, all of which are alike. –A molecular formula gives the exact number of atoms of elements in a molecule. –Structural formulas show how the atoms are bonded to one another in a molecule.

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–26 Figure 2.18: Molecular and structural formulas and molecular models.

Ionic Bonding-Being Like the Noble Gases All atoms want to have the same number of electrons as the Noble Gases. The Noble Gases have very stable electron configurations. In order to achieve the same electron configuration as the Noble Gases metal atoms will give up electrons to form positive ions (cations) and non-metal atoms will receive or take additional electrons to become negative ions (anions). IONS are charged particles. N becomes N -3 Al becomes Al +3 Cl becomes Cl - O becomes O -2 Mg becomes Mg +2 Na becomes Na + The positive and negative ions are attracted to each other electrostatically.

Putting Ions Together Na + + Cl - = NaCl Ca +2 + O -2 = CaONa + + O -2 = Na 2 O Al +3 + S -2 = Al 2 S 3 Ca +2 + N -3 = Ca 3 N 2 Ca +2 + Cl - = CaCl 2 You try these! Mg +2 + F - = NH PO 4 -3 = K + + Cl - = Al +3 + I - = Sr +2 + P -3 = Li + + Br - = Sr 3 P 2 AlI 3 MgF 2 (NH 4 ) 3 PO 4 KCl LiBr Not NH 43 PO 4

Copyright © Houghton Mifflin Company.All rights reserved. Presentation of Lecture Outlines, 2–29 A model of a portion of crystal.