Periodic table

Periodic Table

  • A Chart of the elements arranged into rows and columns according to their physical and chemical properties

Johann Dobereiner (Law of Triads)

  • States that the atomic weight of the middle element in a triad was approximately the average of the atomic weight of the first and third elements

  • Groups of 3 elements with similar properties

John Newlands (Law of Octaves)

  • When elements are arranged in increasing atomic mass, the properties of elements repeats for every 8 elements

Dimitri Mendeleev

  • Elements are arranged according to increasing atomic mass = periodic repetition of properties

  • Elements in the same column have similar properties

Julius Meyer

  • Published a graphical presentation of the periodic table of elements arranged according to increasing atomic mass

Henry Moseley

  • Elements in the periodic table are arranged according to increasing atomic number

Organizing the Periodic Table

  • Groups/Families- Vertical columns of elements that have similar characteristics

  • Periods- horizontal rows in the tables

4 section in the Periodic Table

  • s-block elements- the valence electrons are in the s-blocks, classified as Representative elements/group A

  • p-block elements- the valence electrons are in the p-blocks, classified as Representative elements/group A

  • d-block elements-the elements electrons that are filling up the d-orbital. classified as transition metals

  • f-block elements- fills up f-orbital, classified as inner transitional metals
    4f- Lanthaide Series
    5f- Actinide Series

Representative Elements (Group A)

  • Elements with Valance electrons in the s/p-orbital

  • Group number = Valence electron

  • Period number = Outermost shell

  • Can donate / gain electrons during a chemical reaction to attain octet

  • Octet Rule- for an atom to become stable it must have 8 electrons in the valence shell

Transition Metals (group B)

  • Elements with valaence electrons in the d-orbital

  • Group Number - Depends on the number of electrons in the d-orbital

  • Period number = +1

  • Valence electrons = +2

Inner Transitions Metals

  • Elements with the last electron in the f-orbital

  • group number = depends on the sublevel

  • Pd. no. = +2

Periodic Trends

  • specific patterns in the properties of chemical elements that are revealed in the periodic table

Shielding Effect

  • Electrons are attracted by the nucleus (+) but repelled by the other electrons

  • Thus the electrons “shield” other electrons from the nucleus of the atom

Nuclear Charge

  • its a measure of the ability of protons in the nucleus to attract the negative electrons in orbit around the nucleus

Atomic Radius

  • distance from nucleus to outermost cloud of electrons

  • determines the size of the element

  • As you go down a family the N value increases making the radius longer

  • As you go across a period the number of protons increases, pulling the electrons in tighter making the radius smaller

  • increases left to right and up to down

Ionic Radius

  • radius of an atom’s ion found in a crystal lattice

  • positive ions become smaller than their neutral ions while negative ions are larger than neutral ions

  • increases going down increases going left

  • for metals the nuclear charge is greater than the nnumber of electrons pulling them, making the radius smaller

  • for non-metals,the the radius gets larger because they gain electrons

Electronegativity

  • The tendency of an atom to attract a shared pair of electrons toward itself

  • the higher the electronegativity of an atom the greater the attraction for bonding electrons

Electron Affinity

  • the ability of an atom to accept an electron

  • Elements with almost complete electrons in the subshells have low-affinity values but are relatively stable

Reactivity

  • tendency of an atom to react with other elements

  • higher reactivity means being more prone to chemical destruction or corrosion

  • metals lose electrons when they react, so metals reactivity is based on the lowest ionization energy (bottom left corner)

  • non-metals gain electrons when they react, so non-metal’s reactivity is based on high electronegativity

Metallic Character

  • metalistic luster, high density, high thermal conductibity and high electrical conductivvity