The Periodic Table

Dmitri Mendeleev Created a table arranged by increasing atomic mass and chemical characteristics Wrote the periodic law - Chemical physical properties of the elements are a periodic function of their atomic mass. Predicted the characteristic of three undiscovered elements, Germanium, Gallium and Scandium

    Mendeleev sorted the elements by similar properties, and then by increasing atomic mass. So elements 1, 9, 17, 25, all had similar properties. Each column or family had Its own set of characteristics. He saw that there should be an element with the weight of 12 and it should also Have the characteristics of elements 4, 20, and 28.

Problems  Not all the element fell into place as they should, but it was the best table at the time.

Henry Moseley  Found a way to count protons  Then the table was then rearranged according to increasing atomic number.  ( # of protons)  This removed the problems in Mendeleev’s table.

How is the table arranged?

What are? MetalsNonmetalsMetalloids Active metals noble gases noble gases Transition metals Halogens Alkali and alkaline earth metals

Atomic radius and how it varies

General pattern

Ionization and atomic size  X + energy → X + + e -  An ion is a charged particle ( positive or negative)  Anion = negative cation = positive  The energy required to make a + ion is called ionization energy.

 The smaller the atomic radius the harder it is to remove an electron. ( explain)  Electrons (-) closer to the nucleus(+) are held more strongly.  Pattern on the table, as you move down a family ionization energy gets lower.  As you move left to right ionization energy gets higher.

Ionization energy

Successive ionization energy  It is all ways harder to remove the second and third electron, do to the fact the same number of protons is now holding fewer and fewer electrons.  And some times messing with a more stable electron configuration.

Atomic radius verse ionic radius  + ions are smaller than their parent atom  - ions are larger than their parent atom. Why? Its related to the number of protons and electrons present.

Atomic and ionic radii

Electronegativity  The measure of an atoms attraction for a shared electron.  Similar to ionization energy, it is still a measure of an atoms attraction for electrons.  Pattern on the table is the same.

Electron affinity  The energy released when an atom gains an electron.  X + e - → X - + energy  Opposite of ionization energy