1. The purpose and history of the periodic table.

The purpose of the periodic table is to organize elements into the same group and period, as well as atomic mass and atomic number. The Russian chemist Dmitri Mendeleev arrange elements according to their atomic mass. Based on the textbook, he noticed that when the elements were arranged in order of increasing atomic mass, certain similarities in their chemical properties appeared at regular intervals. The later on, an English scientist Henry Moseley, who was working with Rutherford discover that elements in the periodic table fit into pattern better when they are arranged in increasing order of nucleus charge, or number of protons or neutrons.

 

2. The arrangement of the periodic table.

There are many ways that the periodic table are organized. The first thing is that they are organized in group and period. Group is a column, while period is a row. Each group shares the same properties: valence electrons, reactivity. Period also share similar properties in that they have same number of orbitals(shells). Toward the left side, the elements are metal and is in the s-block elements. In the middle, those elements are metals as well and is in d-block elements. Nonmetals and metalloids are on the right side, p-block elements. Lastly, the f-block elements, which is the actinide and lanthanide.

 

3. Trends about which you have learned using the periodic table (explain at least 2 of them).

Ionization energy- Is the energy required to remove one electron from an atom. Ionization energy increases across the period because of increasingly nuclear charge and also moving up in a group. A higher charge more strongly attracts electrons. So more nuclear charge=more ionization energy=decrease in atomic radii. For example, Group 1(Alkali metal) have low ionization energy because they are reactive and lose electrons more easily. While in Group 18(noble gases), have high ionization energy because they are less reactive and don’t lose electrons easily. However, ionization energy decreases as moving down the group because electrons are removed more easily. There are also more orbitals= more electrons= more shielding in the outer electron from nuclear charge. Therefore, fluorine has the highest ionization energy.

 

Atomic radius- Is the ½ distance between the nucleus of identical atoms that are bonded together. Atomic radius decreases(smaller) as you move across the period because it of increasing positive charge of the nucleus. As electrons are added to s and p sublevel, they are pulled closer to the more highly charge of the nucleus. Atomic radius increases as you move down the group=more electron clouds=more shielding=more effective nucleus charge. The element that is on the furthest to the left in the period has the largest atomic radius because atomic radii decreases across the period.