Bohr and Lewis electron dot diagrams

Bohr and Lewis electron dot diagrams

Bohr and Lewis diagrams are diagrams of elements that the valence electrons for each element are drawn. These electrons are the electrons that are shared or given away in covalent and ionic compounds. They include the "s" and "p" energy list. To draw a dot diagram you write the symbol for and element and draw a dot for evey valence electrons not putting two electrons beside each other until all sides of the element at least have one.



Lewis Diagram of Chlorine

For a video reference: http://www.youtube.com/watch?v=y6QZRBIO0-o

Electronegativity and Polarity

(Red being the most electronegavite and yellow the least)

Electronegativity and Polarity

Electronegativity is the tendency of an element or atom to attract a bonding pair towards itself in a compound. It can range anywhere between 4(fluorine) and 0.7(francium). The higher the number the more likely that electrons will be pulled towards that element in a compound. When a compound is formed with two different elements depending on the electronegativity the elements become polarized. The symbols + and - mean "slightly positive" and "slightly negative". You read + as "delta plus" or "delta positive". The more electronegative element becomes slightly negatively charged while the less electronegative element becomes slightly positive.

In the compound of Carbon and Fluorine, the more electronegative Fluorine attracts the electron pairs and becomes slightly negative and with the carbon is left with less electrons near it becomes slightly positive.

For more insight try this link: http://www.youtube.com/watch?v=Kj3o0XvhVqQ

Periodic table Trends

Periodic Table Trends

The Periodic Table has more trends than just the similarities in properties of elements in each column. Other trends are present like atomic radius, ionization energy, eletron affinity, and electronegativity. As can be seen in the image there are many trends on the periodic table.

Atomic radius is the distance between the outter most electrons and the nucleus. Since the farther down you get on the periodic table the more energy levels are present in the atom, there is a tendency as you move down and to the left on the periodic table to have a higher atomic radius.

Ionization energy is the amount of energy to remove the outter most electron of an atom. When this happens the atom becomes an ion and is positively charged. As you get closer to the top right the more energy you need to remove the outter most electron resulting in a higher ionization energy.

Electron affinity is the amount of energy when an electron joins onto an atom. Electron affinity is not as clear as ionization energy but as you go to the top right of the periodic table electron affinitiy increases.

History of the Periodic Table

History of the Periodic Table



The periodic table shows all the known elements in order of atomic number. Even though the elements listed on the periodic table haven't changed themselves the periodic table has. By 1869 a total of 63 elements had been discovered, and were arranged according to their properties and gaps were left where elements were thought to be missing. The scientist Dimitri Mendeleev was the first to publish a periodic table.



Though the 1869 periodic table looks drstically different than the current day periodic table the elements each have their atomic number and "?" are left where there are elements missing. As more elements were discovered in the 20th century the periodic table became more refined to what it is today.

Electronic Structure of the Atom

Electronic Structure of the Atom Including Electron Configuration and Valence Electrons

Depending on how many electrons an atom has there is a set pattern that the electrons conform to. For each energy level there is a maximum amount of electrons that can be in them. For the "s" there can only be two electrons, "p" can have six elecrtrons, "d" can have ten electrons, and "f" with the most energy can have fourteen electrons within it. For instance elements within the second row of the periodic table can have their electrons written out as 1s^2 2s^2 2p^6.

Along side the electron configuration valence electrons are introduced. These are the electrons in the outter most, uncomplete shells of the "s" and "p". The electrons in these uncomplete energy levels are the electrons that are used in ionic and coavalent compounds. Also since only the "s" and "p" energy levels are taken into account for the valence electrons the maximum amount of electrons in the valence shell is eight.

Structure of the Atom

Structure of the Atom

An atom consists of neutrons, protons, and electrons. Protons are positively charged and electrons are negatively charged. The electrons orbit around the nucleus, that consist of protons and neutrons.

In terms of mass, neutrons and protons contribute the most to the total mass of an atom. Electrons, in comparison to the neutrons and protons in the nucleus, don't affect the total mass of the atom.

History of the Atom

History of the Atom

Around 460 B.C.E. a Greek philosopher Democritus first questioned the existence of atoms. He thought the atom was a sphere with barbs on the surface that held it together with other atoms. Not until about the 1800's though did the idea of the atom become revised. John Dalton was the first modern scientist to look at the fact that matter was made up of atoms.

J.J. Thomson's atomic model

In 1897 J.J. Thomson discovered the electron and proposed the "Rasin in Pudding" model of the atom. It showed a sphere with electrons attached on the outside in random posistions.

 Ernest Rutherford's atomic model

In 1911 Ernest Rutherford sent alpha rays from Radium through gold foil and discovered most of the rays went through the foil. He then brought him to believe that in an atom there are empty spaces between the electons and the nucleus.

Niels Bohr's atomic model

In 1912 Niels Bohr stated a theory of why electrons did not spiral into the positive part of an atom and stated that electrons occupy shells around the nucleus.