Chem 111 Ch. 2

2.1 The Structure of the Atom

• Atoms consist of three subatomic particles

  • Protons, Neutrons, and Electrons

    • Proton - Relative charge of +1 and has a mass of $1.672622\times10^{-24}$

    • Neutron - carries no electrical charge and has a mass of $1.674927\times10^{-24}$

    • Electron - carries a relative charge of -1 and has a mass of $9.109383\times10^{-27}$

• Protons and Neutrons are found in the atomic nucleus

  • Electrons are around the nucleus

• The mass and charge of an atom affects the physical and chemical properties of the element and the compounds it forms

• Atomic Mass Unit (u): defined as 1/12 the mass of a carbon atom that containst six protons and neutrons

  • protons and neutrons are both one u

    • electrons are about 2000 times less than that of protons and neutrons. approx 0

• Atoms with an unequal number of protons and electrons are called ions.

  • cation - positive atom

  • anion - negative atom

Atom Characterization

• Atomic number (Z) = number of protons and neutrons

  • Neutral atoms’ atomic number would also equal the no. of electrons in that atom

• Mass number (A) = mass of protons and neutrons in atomic mass units (u)

• Neutrons = mass number - Atomic Number

• Atomic Symbol - letter symbol

  • Ex: Carbon is $\frac{12}{6}C$ (6 neutrons and 6 protons) and Gold is $\frac{198}{79}Au$ (79 protons and 119 neutrons)

Isotopes and Atomic Weight

• Neutron numbers may vary its not always the same as the proton count

  • Atoms that have the same atomic number (Z) but differnet mass numbers (A) are called isotopes

    • Isotopes are named using the ement name and the mass number

      • Carbon-12, Carbon-13 are also $^{12}C$ and $^{13}C$

• Due to the existence of isotopes, the mass of collection of atoms of an element has an average value

  • Average mass = Atomic Weight

• Atomic Weight = Abundance of Isotope A $\cdot$ Mass of isotope A + Abundance of isotope B $\cdot$ Mass of isotope B + …

  • ABUNDANCE OF ISOTOPES HAS TO BE 100%

Periodic Table

• Groups move down

• Periods move across

• 1A - Alkali Metals

  • Shiny malleable (Squishy) substances

  • excellent conductor for electricity and heata

  • react violently with water to form strong basic solutions

  • Lose electron to form cations

• 2A - Alkaline Earth Metals

• 7A - Halogens

  • non metals

  • do not conduct electricity

  • Highly reactive

  • Form strong acids w water

  • gain electrons to form anions

• 8A - Noble gases

  • Difficult to react with  

Valence Electrons and Ionic Compounds

• All elements have certain number of total electrons

• Can be separated onto two types

  •   Core

    • Any other electron lcated deeper in the shell

  • Valence

    • Electrons in the outermost ring

• For a main group elemnt, the nunmber of valence electrons is the same as the group number

Compounds

• Combo of atleast 2 or more atoms of different elemetns bonded together in a defined ratio

  • AB or AB2 or A2B

• Phy and Chem characteristics of compounds differ from props of individual elements that make the compound

Ionic ompounds

• Held together by attractiove foces between ations and anions

• Cations (X^+) pos charged ion

• Anions

  • Bond created is called ionic bond

• Generally formed between Metals and nonmetals

(ex: Na pos Cl neg)

Predicting Ion’s Charge

• Octet Rule

  • Atoms all want a full outermost shell of 8 valence electrons

• In general

  • Metals lose electrons forming cations

  • Non-metals gain electrons forming anion

Monoatomic Ions

• When an atom gains or looses electrons monoatomic ions are formed (containing only 1 atom)

Naming Monoatomic Ions

• Cations: name of element followed by ion

  • K^+ = Potassium ion

• Transition Metal cations: element followed by charge in roman numerals then ion

  • Cr²+ = Chromium (II) ion

  • Anions: the first part of eleemnt name ollowed by suffix-ide, followed by ion

  • Br^-: Bromide Ion

Polyatomic Ions

• group of atoms that have a charge

  

• Naming Ionic Compound Formulas

  • Rpresented by the simplest ratio of cation to anion

  • Rule 1: in an ionic compound CATION IS WRITTEN FIRST THEN ANION

  • rule 2: IN neutral ionic compounds TOTAL cationic positive charge is BALANCED by TOTAL anionic negative charge

            (always end up neutral)

Ionic Compounds

• Simple rule: the magnitude of the charge on each ion is used as the subscript fir the other ion in the fomrula for the substance

  • charge is turned into subscript opposite

• Barium Chloride

  • Ba²+ Cl^-1

    • BaCl₂

• Aluminum Oxide

  • Al₂O₃

Formula to name

• Ionic Compounds: Cation name + Anion name, “ion” is dorpped, prefixes are not used to indicate the number of ions

  • Sodium Nitrate - NaNO₃

  • Cobalt (III) Oxide - Co₂O₃

  • Iron (III) Chloride - FeCl₃

  
  

• KCI Potassium Chloride K+ Cl-

• CoO Cobalt (II) Oxide Co²⁺ O^2-

• BaI₃ Barium Iodide. Ba²⁺ I^-

• FeBr3

Name to Formula Practice

(Lithium Phosphate)

• Li₃PO₄

Iron (III) Perchlorate

Fe³⁺. ClO₄^-

Fe(ClO₄)₃

Practice Formula to Name

AlPO₄

Aluminum Phosphate

Fe(MnO₄)₃

Iron (III) Permanganate

COVALENT COMPOUNDS

• Reminder: Ionic bonds are trasnferred electrons, sharing of electrons are Covalent Bonds

• Line between two nonmetals represents the shared electron bonding both atoms

• Representing Covalent compounds

  • Molecule formula - H₂O

  • Structural Formula - H - O - H. shows connectivity

  • Ball and Stick - showw geometry

  • Space filling model -

  • Cluster of water molecules

• Molecular Covalent Compounds

  • H2O

• Network covalent compounds

  • Atoms held together by a network of covalent bonds

  • Ex: Diamond

NON METALS - COVALENT MOLECULES

METALS - IONIC MOLECULES

Naming Compounds

1. first element is named first, followed by second element using the -ide ending as in the nomenclature for salts

2. Use prefixes to show the number of each type of atoms

3. do not use mono on first element

Ex: BCl₃

Boron trichloride

N₂O₃

Phosphorus Triiodide

Carbon Tetrabromide

INORGANIC ACIDS

• Produce protons (H⁺) when dissolved in water

• Usually Hydrogen is the first element in the formula of inorganic acids

HYDROCARBONS

• Basic organic molecules like CH₄ (Methane) C₂H₆ (Ethane),