The+Periodic+Table+of+Elements



**The Periodic Table of Elements** is the most wildly accepted way of organizing the know chemical elements of the universe into a structured and helpful chart. It is used in many fields of science including Chemistry, Biology, and Physics. It is divided into horizontal rows, or periods, and vertical columns, also called groups or families. There are 9 periods and 18 families. The periodic table of elements contains 118 chemical elements that have been discovered, each element can be found in a box at the intersection of a row and a column.


 * __**When was the modern periodic table created and by whom? **__


 * __**How are the elements on the periodic table organized? **__


 * __**What are some trends that can be found in the periodic table? Please describe them. **__

Rinad Bakhti: (1) Periodic table was created by Dmitri Mendeleev in 1869. (2) Each vertical column refers to a family or group in the periodic table. The horizontal rows are called periods. (3) The trends available are similarities of properties between elements of the same columns or rows.

Ibrahim Halawi: 1. Created by Dmitri Mendeleev in 1869. 2. Vertical column is called a family/group, the horizontal rows are named periods 3. SImilarities of properties from element to element of the the same row (period) or column (family)

Najla Awayda: (1) in 1869 by a Russian Chemist - Dmitri Mendeleev. (2) The elements in columns, called groups, have the same number of electrons in the their outer orbital. The elements in the center section, transition elements, have special electron rules. The elements in rows, called periods, have the same number of atomic orbitals, the maximum number of orbitals for any element is seven. (3) The ordering of the elements allows you to predict some of the properties of the elements relative to each other : Atomic radius - half of the distance betwen the centers of two atoms that are touching each other (decreases moving left to right, increases moving top to bottom) Electron affinity - alkaline earth, halogens, noble gases. Ionization enegry - energy required to remove an electron ( increases moving left to right, decreases moving top to bottom) Electronegativity - measure of the attraction to form a chemical bond (increases moving left to right, decreases moving top to bottom)