Unit #1: Matter

Isotopes:

• Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons

Periodic Trends:

• Atomic radius:

  • Definition - distance from the nucleus to the outer most electron 

  • Trend across a period - decrease across a period, more proton pull electrons closer (this is due to the increase in attraction between the electrons are at the same energy level and distance, and an increasingly positive nuclear core)

  • Trend down a group- increase down a group, more electron shells added = larger size (increase in electron energy levels and repulsion between the electrons in different energy levels (shielding))

• ionization energy:

  • Definition - energy required to remove on electron from a neutral atom  (formation of cations)

  • Trend across a period - increase across a period, stronger attraction to nucleus = harder to remove electrons (with the increase in protons there is a greater attraction between the electrons increasing positive nuclear core)

  • Trend down a group - decrease down a group, outer electrons are farther from the nucleus = easier to remove electrons (electrons in the lower energy levels shield the electrons further away from the nucleus reducing their attraction to the core of the atom) (this makes it easier to remove the outer electrons)

• Electrnegavity:

  • Definition: Relative strength of attraction of an atoms nucleus to a bonding pair of electrons

  • Trend across period: increases (atoms with an increasing nuclear core have a stronger attraction to bonding pairs of electrons)

  • Down the group: it decreases (the lower the energy electrons shield the higher the energy electrons) (the higher energy electrons which would participate in bonding would then be less attracted to the nucleus)

• Electron Affinity:

  • Definition: energy released when an electron is added to a gaseous atom (formation of anions)

  • Trend across period: electron affinity increases (atomic size decreases causing the attraction between the nucleus and incoming electrons stronger)

  • Down the group: electron affinity decreases (the added electron is further from the nucleus, experiencing less attraction)

Lewis Dot Structures:

• Simplified Bohr Rutherford diagrams

• Only symbol of the element is used and the most important electrons, the ones in outermost orbit

• Ions are formed when an atom has an uneven number of protons and electrons

• An ion with more protons than electrons is positively charged (cation)

• An ion with more electrons than protons is negatively charged (anions)

• To show a cation as a Lewis structure you must show the charge the atom becomes as a stable ion

• To show an anion as a Lewis structure you must show the charge the atom becomes as a stable ion

  Covalent Compounds:

• Formed when bonding atoms share electrons to become stable

• Electrons participate in bonding are usually found in the highest energy level

Chemical nomenclature:

• Monovalent compounds (ionic compounds that contain cations with only one oxidation number)

  • name of the cation is kept the same

  • Name of the anion is changed to end in ide

  • Write down ion symbols

  • Write down oxidation number

  • Crossover oxidation number only

  • Simplify ratio ions if possible

• Multivalent compounds: ionic compounds that contain cations with more than one oxidation number

  • the name of cation is same

  • A Roman numeral is used to represent the oxidation number of the anion

  • The name of the anion is changed to end in ide

  • Write down ion symbols

  • Write down oxidation number of the ions use Roman numeral for cation

  • Crossover oxidation number

  • Simplify

• Polyatomic compounds: ionic compounds which contain cations or anions with more than one element

  • the name of the cation is used

  • Roman numerals are used if polyvalent cation is present

  • Name of anion is used

  • Write down ion symbols

  • Write down the oxidation number only

  • Simplify

• Covalent compounds: molecular comptines (2 or more non metals)

  • the name of the less electronegative element is kept the same (if greater than one atom is present a prefix is used)

  • The name of the more electronegative element is changed to have a prefix added and the end is changed to ide

  • Write down symbols

  • Add appropriate subscript using prefix

• Hydrated salts: ionic compounds that have water within their crystalline structure

  • appropriate name of compound

  • Number of water molecules is represented by a prefix followed by hydrate

  • Write down the formula for the compound

  • Add the coefficient for the number of water molecules

• Binary acids: acids which contain hydrogen and one other element

  • the prefix hydro is used

  • Other element name changed to end with ic acid

  • Write down ion symbols

  • Write down oxidation number

  • Crossover

  • Simplify

• Oxyacids: acids which contain polyatomic oxyanions

  • Base oxyanion end in age

  • Changes when they contain additional or fewer oxygen atoms

  • Use appropriate oxyanion prefix and ending

  • Hypo ite changes to hypo ous

  • Ite changes to ous

  • Ate changes to ic

  • Per ate changes to per ic

  • Add word acid

  • Write down ion symbols

  • Write down oxidation number

  • Crossover

  • Simplify