- Periodic Table of Elements DIMendeleev
Periodic system is a multi-storey "house", which houses a large number of apartments.Each "resident" or chemical element of living in your own apartment at a certain number, which is permanent.Besides element has a "name" or the name, such as oxygen, nitrogen or boron.In addition to these data in each "house" or cell contains information such as relative atomic mass, which can be exact or rounded values.
As in any home, there are "entrances", namely the group.And the elements are arranged in groups on the left and the right, forming a subgroup.Depending on which side of their longer that subgroup called the principal.Another subgroup, respectively, will be incidental.Al
so in the table are "floors" or periods.Moreover periods may be either larger (composed of two rows) and low (they have only one row).
On the table can show the atomic structure of elements, each of which has a positively charged nucleus composed of protons and neutrons, as well as orbiting negatively charged electrons.The number of protons and electrons is numerically the same as defined in the table and on the atomic number.For example, a chemical element sulfur №16 has, therefore, will have 16 protons and 16 electrons.
To determine the number of neutrons (neutral particles, also located in the nucleus), subtract the relative atomic mass of the element in its serial number.For example, iron has a relative atomic mass equal to 56 and the sequence number 26. Therefore, 56 - 26 = 30 protons in iron.
Electrons are at different distances from the nucleus, forming the electronic levels.To determine the number of electronic (or energy) levels, you need to look at the number of the period in which the item is located.For example, aluminum is 3 period, therefore, it will have three levels.
According to the group number (but only for main group) can be determined the higher valence.For example, the elements of the first group of the main group (lithium, sodium, potassium, etc.) have a valence of 1. Accordingly, the elements of the second group (beryllium, magnesium, calcium, etc.) will have a valency equal to 2.
Also on the table it is possible to analyze the properties of the elements.From left to right the metallic properties are weakened, and non-metallic reinforced.This is well illustrated by two periods: starting with an alkali metal solution, then the alkaline earth metal magnesium, after an amphoteric element of aluminum, then non-metals silicon, phosphorus, sulfur and ends between gaseous substances - chlorine and argon.In the next period, a similar dependence.
top to bottom and there is a pattern - metallic properties are enhanced and nonmetallic weaken.That is, for example, cesium is much more active in comparison with sodium.
For convenience, better to use a color version of the table.