Atoms-Molecules-Ions Dr. Ron Rusay Spring 2008 © Copyright 2008 R.J. Rusay

Aspects of Matter Elements, Compounds, and Mixtures (Part 1) Atomic Theory Today Elements: The Periodic Table Ions & Compounds Compounds: Introduction to Ionic Bonding Compounds: Formulas & Names (Part 2) Mixtures: Separation Techniques (Part 3) Atomic & Molar Masses (Part 4)

Modern History of the Atom  1909: Millikan determines charge and mass of e-  : Rutherford & Bohr’s atom; The proton.  1927: Waves & Particles, Quantum Mechanics  1932: James Chadwick “discovers” the neutron © Copyright R.J. Rusay

CHEMISTRY of the Atom Ernest Rutherford ( )

Modern History of the Atom 1897: J.J. Thomson “discovers” the electron: Photo © The Nobel Foundation © Copyright R.J. Rusay

Milliken Oil Drop Experiment

How does an atom relate to nanotechnology? Consider Powers of 10 (10 x ) Earth = 12,760,000 meters wide (12.76 x 10 6 ), million meters (megameters) Plant Cell = meters wide (12.76 x ) (12.76 millionths of a meter) (12,760 nanometers!) Nano scale is regarded as < 1,000 nanometers ~1/50 the diameter of a human hair (anything less than a micron (10 -6 m). Chemists typically think in views and images of < 1 nanometer (eg. bond lengths and atomic sizes).

1 nm = 10 Å An atom vs. a nucleus ~10,000 x larger ~ 0.1 nm Nucleus = 1/10,000 of the atom Anders Jöns Ångström ( ) 1 Å = 10 picometers = 0.1 nanometers = microns = centimeters

1 nm = 10 Å An atom vs. a nucleus ~10,000 x larger Can we “see” and manipulate atoms using a microscope? Yes, using atomic force microscopy (AFM) and a variety of instruments such as Scanning Transmission Electron Microscopes. TEAM 0.5: LBL’s Latest (2008) Transmission Electron Aberration-corrected Microscope Resolution: +/ /- 0.5 Å

Xe atoms on Ni(110) Atomic/molecular structures atom-by-atom STM images courtesy of Don Eigler, IBM, San Jose Building of a quantum “corral” with Fe atoms on Cu

C C H H Calculated image (Philippe Sautet)   orbital pzpz TIP H O + Imaging: acetylene on Pd(111) at 28 K Molecular Image Tip cruising altitude ~700 pm Δz = 20 pm Surface atomic profile Tip cruising altitude ~500 pm Δz = 2 pm 1 cm (± 1 μm) The STM image is a map of the pi-orbital of distorted acetylene Why don’t we see the Pd atoms? Because the tip needs to be very close to image the Pd atoms and would knock the molecule away If the tip was made as big as an airplane, it would be flying at 1 cm from the surface and waving up an down by 1 micrometer M. Salmeron (LBL)

Excitation of frustrated rotational modes in acetylene molecules on Pd(111) at T = 30 K Tip e-e- ((( ) ( ))) M. Salmeron (LBL)

CHEMISTRY of the Atom FUNDAMENTAL PARTICLES: Mass ChargeSymbol Mass ChargeSymbolNucleus:  PROTON 1 amu +1 H+, H, p 1.67 x kg 1.67 x kg  NEUTRON 1 amu 0 n 1.67 x kg 1.67 x kg_________________________________________  ELECTRON very small -1 e -  2000 x smaller than a proton or neutron  2000 x smaller than a proton or neutron The particle is said to “hold” or “bond” atoms together in molecules. © Copyright R.J. Rusay

Periodic Table © Copyright R.J. Rusay Mendeleev’s Table Mendeleev’s Table Mural at St.Petersburg University, Russia

QUESTION The element found in the 6A family (or group 16) and period four can be toxic and a micronutrient. What is the symbol for that element? You can use any help aid to answer this question except a breathing resource. 1.Sb 2.As 3.Se 4.Te

ANSWER Choice 3 pinpoints an element in both the 6A column and row four. Remember to include the first row of Hydrogen and Helium when counting rows. Section 2.7: An Introduction to the Periodic Table

Chemical Symbols & Historical Names What is the symbol for gold and what was its original name?

QUESTION

ANSWER 1) Phosphorus, Pr Section 2.7 An Introduction to the Periodic Table ) (p. 55 Phosphorus has a symbol of P. 1)Phosphorus, Ph Section An Introduction to the Periodic Table

QUESTION Of the following which would not be considered a metalloid? 1.Ge 2.Sb 3.Se 4.Spockonium, element #182 in the Star Trek Periodic Table.

ANSWER Choice 3, Se, is the only element (without considering the possibility of the fictional Spockonium) listed that is not on the accepted Periodic Table’s “stairway” between metals and nonmetals, therefore it is the only non-metalloid listed. Section 2.7: An Introduction to the Periodic Table

Periodic Table  Elements are classified by: properties & atomic number properties & atomic number metals, non-metals, metalloids metals, non-metals, metalloids  Groups or Families (vertical) 1A = alkali metals 1A = alkali metals 2A = alkaline earth metals 2A = alkaline earth metals 6A (16) = chalcogens 6A (16) = chalcogens 7A (17) = halogens 7A (17) = halogens 8A (18) = noble gases 8A (18) = noble gases  Periods (horizontal) numbers 1-7

Group 1 and Group 2 Metals

Using the Periodic Table

Atoms, Molecules & Ions  Atoms (neutral electrostatic charge: # protons = # electrons ) # Protons = Atomic Number# Protons = Atomic Number Atomic Mass = # Protons + # of NeutronsAtomic Mass = # Protons + # of Neutrons Isotope: same atomic number but different atomic mass (different # of neutrons)Isotope: same atomic number but different atomic mass (different # of neutrons) © Copyright R.J. Rusay

QUESTION

ANSWER ) 4)a, d and b, e Section 2.5 The Modern View of Atomic Structure: An Introduction(p. 49 Isotopes have the same number of protons and different numbers of neutrons, so they can be organized by atomic number.

Atoms, Molecules & Ions Isotopes vary in their relative natural abundance.Isotopes vary in their relative natural abundance. Periodic Table’s atomic mass is a weighted average of all isotopic massesPeriodic Table’s atomic mass is a weighted average of all isotopic masses The mass of sodium, Na, element #11 is listed as amu. Which isotope is naturally present in the larger amount: the isotope with 12 neutrons or with 13 neutrons? (There is a small percentage of the isotope with 11 neutrons.)The mass of sodium, Na, element #11 is listed as amu. Which isotope is naturally present in the larger amount: the isotope with 12 neutrons or with 13 neutrons? (There is a small percentage of the isotope with 11 neutrons.) © Copyright R.J. Rusay

Atoms, Molecules & Ions  Atomic Mass of Carbon:  What is the “weighted” atomic mass? © Copyright R.J. Rusay x 98.98/ x = =

Atoms, Molecules and Ions © Copyright R.J. Rusay Atomic Number = 6 (atom’s identity)Atomic Number = 6 (atom’s identity) CarbonCarbon Atomic Mass = 13 (isotope 13)Atomic Mass = 13 (isotope 13) 6 protons; # neutrons = protons; # neutrons = neutral atom has 6 electronsneutral atom has 6 electrons

QUESTION

ANSWER 1)0%. Section 3.1 Atomic Mass (p. 77) The is an average of the isotopic masses. None of the isotopes has an exact mass of

Atomic Symbols K  Element Symbol Mass number  Atomic number  Also written as  39 K

Atoms, Molecules and Ions © Copyright R.J. Rusay Atomic Number = 12 (atom’s identity)Atomic Number = 12 (atom’s identity) Atomic Mass = 24Atomic Mass = protons; # neutrons = protons; # neutrons = neutral atom has 12 electronsneutral atom has 12 electrons Ion contains 10 electrons: symbol?Ion contains 10 electrons: symbol? 12 p e - = +212 p e - = +2

Atoms, Molecules and Ions © Copyright R.J. Rusay Atomic Number = 17 (atom’s identity)Atomic Number = 17 (atom’s identity) Atomic Mass = ?Atomic Mass = ? # protons = ? ; # neutrons = ?# protons = ? ; # neutrons = ? neutral atom has ? electronsneutral atom has ? electrons Ion contains 18 electrons: symbol?Ion contains 18 electrons: symbol? 17 p e - = -117 p e - = -1

Ions  Cation: A positive ion  Mg 2+, NH 4 +  Anion: A negative ion  Cl , SO 4 2   Ionic Bonding: Force of attraction between oppositely charged ions.

QUESTION Calcium plays several critical roles in the functioning of human cells. However, this form of calcium is the ion made with 20 protons and 18 electrons. Therefore the ion would be… 1.positive and called an anion. 2.positive and called a cation. 3.negative and called an anion. 4.negative and called a cation.

ANSWER Choice 2 provides the correct relationship and name for an atom of calcium (20 protons = 20+) that has lost two electrons (now with 18–). The ion would have a +2 charge. Positive ions are called cations. Section 2.6: Molecules and Ions

QUESTION Of the following, which would NOT qualify as an isotope of 35 Cl? Cl Cl – Cl – Cl

ANSWER Choice 2 is NOT an isotope of 35 Cl. All three choices represent a form of chlorine but choice 2 has the same number of neutrons as the atom in the question, therefore it does not fit the criteria for isotopes (i.e. variable neutron number with constant proton number). Isotopes can be ions as well as neutral atoms. 37 Cl – and 37 Cl are also not isotopes. Section 2.5: The Modern View of Atomic Structure: An Introduction

Worksheet: Atoms I Lab Manual: Pg. 157 Lab Manual: Pg. 157

Polyatomic Ions

Molecules  Neutrally Charged  Eg. Salt: NaCl -> 1 Na + and 1 Cl -  What is the proportion of ions for a compound formed from Mg ion and chlorine?  Mg 2+ and Cl   1 Mg 2+ combines with 2 Cl 

Ionic vs. Covalent

 Metals generally combine with non- metals to form ionic compounds. Electrons are “lost” by the metal and “gained” by the non-metal following the octet rule.  Non-metals generally combine with non- metals to form covalent compounds where electrons are “shared”. Each pair of electrons ia a covalent bond. Eg. H 2 O  Polyatomic ions have both covalent and ionic properties. Eg. hydroxide, OH -

QUESTION

ANSWER 2.6) 2)Ions are formed by changing the number of protons in an atom’s nucleus. Section Molecules and Ions(p. 52 The removal of a proton from the nucleus requires extraordinary amounts of energy. It will only happen during a nuclear reaction.

Chemical Formulas  Molecular Formula: Elements’ Symbols = atoms Elements’ Symbols = atoms Subscripts = relative numbers of atoms Subscripts = relative numbers of atoms  How many atoms of each element are in the following componds? MgCl 2 CCl 4 NaOH (NH 4 ) 2 CO 3 C 20 H 26 N 2 O (Ibogaine, not ionic)

QUESTION

ANSWER 4) 8 Section 2.8 Naming Simple Compounds(p. 57) Remember to multiply the number of oxygen atoms in the parentheses by the subscript outside of the parentheses. 4) 8 Section 2.8 Naming Simple Compounds(p. 57 Remember to multiply the number of oxygen atoms in the parentheses by the subscript outside of the parentheses.