periodic table molar mass electronegativity

This is approximately the sum of the number of protons and neutrons in the nucleus. The mass of an atom relative to that of carbon-12. The transition of a substance directly from the solid to the gas phase without passing through a liquid phase.ĭensity is the mass of a substance that would fill 1 cm 3 at room temperature. The temperature at which the liquid–gas phase change occurs. The temperature at which the solid–liquid phase change occurs. The arrangements of electrons above the last (closed shell) noble gas. These blocks are named for the characteristic spectra they produce: sharp (s), principal (p), diffuse (d), and fundamental (f). The atomic number of each element increases by one, reading from left to right.Įlements are organised into blocks by the orbital type in which the outer electrons are found. Members of a group typically have similar properties and electron configurations in their outer shell.Ī horizontal row in the periodic table. Therefore the distinguishing electron must occupy either the 5 s or 5 p subshell.A vertical column in the periodic table. For example, iodine is a representative element in the fifth period. The value of n, the principal quantum number for the distinguishing electron, can be quickly determined by counting down from the top of the periodic table. As a general rule, in the case of the representative elements, the distinguishing electron will be in an ns or np subshell. In the third period the 3 s subshell is filling for Na and Mg, and therefore Al, Si, P, S, Cl, and Ar. Across the second period Li and Be have distinguishing electrons in the 2 s subshell, and electrons are being added to the 2 p subshell in the atoms from B to Ne. In the first period the distinguishing electrons for H and He are in the 1 s subshell. The first three horizontal rows or periods in the modern periodic table consist entirely of representative elements. Formulas for chlorides of the first dozen elements that show the periodic variation of valence Element This agrees with the valence rules derived from the periodic table, and results in formulas for chlorides of the first dozen elements that show the periodic variation of valence.

For representative elements the number of valence electrons is the same as the periodic group number, and the number needed to match the next noble-gas configuration is 8 minus the group number. That is, the valences of the representative elements may be predicted on the basis of the number of valence electrons they have, or from the number of electrons that would have to be added in order to attain the same electron configuration as an atom of a noble gas. Many of the chemical properties of the representative elements can be explained on the basis of Lewis diagrams. Most of the elements whose chemistry and valence we have discussed so far fall into this category. The representative elements are those in which the distinguishing electron enter an s or p subshell. The type of subshell ( s, p, d, f)into which the distinguishing electron is placed is very closely related to the chemical behavior of an element and gives rise to the classification shown by the color-coding on the periodic table seen here. This last electron is called the distinguishing electron because it distinguishes an atom from the one immediately preceding it in the periodic table. Since it is the outermost (valence) electrons which are primarily involved in chemical interactions between atoms, the last electron added to an atom in the building-up process is of far more interest to a chemist than the first. The commonly used long form of the periodic table is designed to emphasize electron configurations.

Periodic table molar mass electronegativity