The Periodic Table

The Modern Periodic Table

• periodic table summarizes a lot of information that is used by chemists

• Basic recap:

  1. symbol for each element is in a singular box

     1. the boxes are listed in increasing atomic number
     2. atomic mass is listed below the symbol

  2. rows in the periodic table are called periods

     1. have 2-32 elements

     2. periods with 32 normally have 14 underneath the periodic table

  3. columns are called groups

     1. elements within the groups have similar physical and chemical properties

     2. the closer the elements are they are more similar

  4. groups are normally numbered

• Atomic Symbols

  • each element is labeled with a one or two letter symbol(Z)
  • most are just abbreviations of their English name
  • 11 elements are from other languages
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  • when symbols are used by chemist they add subscripts and superscripts
  • they describe different atomic properties in each element
  • upper left-hand corner is used for the mass of an isotope (a)
  • lower left hand corner is used for the atomic number
  • upper right hand corner is the charge of the ion
  • when you add and remove electrons in the ion
  • any subscripts used in writing chemical formulas are in the lower right hand corner
• Electron, Protons, and Neutrons
  • you can use the periodic table to figure out the number of electrons and protons
  • neutrons can be calculated only if you have a specific isotopic mass of said element
  • Protons
  • for an element protons always equal to atomic number (Z)
  • Electrons
  • number of electrons in regular element= atomic number (Z)
  • ion number of electrons can be calculated using:
    • Z– charge of the ion
  • positive ion has lost electrons
  • negative ion has gained electrons
  • Neutrons
  • neurons vary on specific isotope of the element
  • atomic masses on the periodic table are weighted averages or all the natural ions of the element
  • normally the neutrons cannot be found using the periodic table
  • if you have the isotopic mass then you can find the number of neutrons using this equation:
    • A–Z
  • Isotopes
  • isotopes are elements that have varying numb res of nuetrons but the same amount of

Radioactivity

• property of matter where the nucleus emits small particles and energy to become more stable
  • its called radioactive decay
• it works like a chain
• some are naturally radioactive isotopes
  • others aren’t
• emit only a couple types pf subatomic particles when jeu disintegrate
• includes the
  • electron(beta particle)
  • neutron
  • helium nucleus (alpha particle)
  • positron
• after the particles are discharged the nuclear mass (A) and/or nuclear charge (Z) changes
• energy can also be released as gamma and X rays
• this energy doesn’t change the isotopes
  • neither ray has charge
• Mass Spectrometry
  • essential instrument for understanding matter back in the day
  • in a high vacuum of a mass spectrometer tiny bits of substances are vaporized and subjected to an electron beam and it creates ions
  • ions are separated and recorded based upon mass to charge ration(m/z) of each ion
  • pattern of mass to charge ratios and intensity Tod each m/e is called a mass spectrum
  • when looking at ions with a singular charge then m/e can just be mass
• Atomic Masses
  • atomic mass on the periodic table is based on the atomic mass of pure C-12
  • exactly 12
  • most elements have 2+ isotopes so the listed mass is an average
  • weighted average= mass of isotope(abundance of isotope)

Periodic Properties of Elements

• lanthanide and actinide series are below the mass of the periodic table
• groups chemist’s use
  • alkali metals
  • alkaline earth metals
  • transitional elements
  • halogens
  • nobel gases
• chemical reactions happen when atoms collide with others
  • in these collisions the valence electrons are to ones effected
  • this is the reason why the chemical properties are sillier correlating to the valence electrons
• similarities happen due to sap,d,f orbitals
  • works with the columns and groups
• a differentiating is the electron that makes the neutral element different from the other ions of the same electron
• isoelectronic refers to ions and atoms that have the exact same electron configuration
• Physical Properties of the Elements
  • out of all the 118 elements only 2 elements are liquids with normal conditions
  • mercury
  • bromine
  • the noble gases are all gases at room temp
  • hydrogen
  • nitrogen
  • oxygen
  • fluorine
  • chlorine
  • all the other elements are solid
  • most of the elements are individual atoms
  • some are naturally occurring as diatomic molecules
  • H2
  • O2
  • N2
  • all the halogens
  • sulfur is usually in S8 and phosphorus in P4 but they are shown as a individual atoms in chemical reactions
• metals and metalloids
  • metals are most of the elements in the periodic table
  • there are metalloids that are elements that are kinda like metals and kinda like nonmetals
• Allotropes
  • elements that has 2+ distinct sets of physical and chemical properties
  • O2 and O3 are allotropes of oxygen
  • diamond, buckminsterfullerene and graphite are allotropes of Carbon
• Variation of Physical properties
  • metallic character of elements increases from top to bottom of whatever group you’re looking at
  • melting and boiling point s of metals often decrease from top to bottom of the groups
  • nonmetals so the opposite
• Atomic Radii
  • atomic radius increases top to bottom of the groups
  • bc of increase in period number= larger energy level
  • when going left to right atomic radius decreases
  • bc effective nuclear charge increases
• Effective Nuclear Charge
  • core electrons- the ones not in the valence shell
  • core elections shield the protect the valence electrons from the positive energy of the nucleus
  • vance electrons don’t protect other valence electrons
• Ionization Energy
  • energy needs to completely remove an electron from an atom
  • always endothermic energy
  • bc energy must be added tp remove the electron
  • removing the 1st electron tells the first ionization energy for most of the elements on the periodic table decrease from top to bottom of a group
  • first ionization energy increases left to right of the period
  • when you remove more than one electrons you can tell that valence electrons have a low ionization energy compare to all the core lectrons
  • shown in this table
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• Photoelectron Spectroscopy
  • when high energy beams are set on element surfaces then electrons may be ejected
  • photoelectric effect
  • photoelectron spectrometers measures the ejected electron’s kinetic energy
  • also bathe sample of light in specific energies
  • the difference between the incoming and outgoing is how strong the electrons are held to the atoms
  • binding energy
  • photoelectron spectra is very hard to read so we often use idealized spectra
  • y axis’s shows that peak sizes are proportional to how many electrons are in the orbital
  • x axis has moistly high energies on the left that decrease down to zero as you go left
  • larger energies- stronger attraction to nucleus
  • lowest- valence electrons
• Electron Affinity
  • energy charge that accompanies the adding of an electron to the atom
  • some atoms attract electrons so the electron affinity os negative bc energy is released
  • majority of atoms don’t just attract electrons so electron affinity is positive bc energy is used to add an electron
  • fluorine highest electron affinity
  • francium lowest electron affinity
• Electronegativity
  • describes the attraction of electrons by singular atoms
  • combo of
    • ionization energy
    • electron affinity
    • other factors
  • the concept is used to determine how electrons are distributed in different molecules
  • trends on periodic table change from left bottom corner to right top corner
• Ionic Radii
  • 2 types pf ions
  • cation
    • lost 1+ electron
    • positive charge
  • anions
    • gained 1+ electron
    • negative charge

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