This fact has key implications for the building up of the periodic table of elements.

The ordering of the electrons in the ground state of multielectron atoms, starts with the lowest energy state (ground state) and moves progressively from there up the energy scale until each of the atom’s electrons has been assigned a unique set of quantum numbers. It is the Pauli exclusion principle that requires the electrons in an atom to occupy different energy levels instead of them all condensing in the ground state. In the periodic table, the elements are listed in order of increasing atomic number Z. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. The configuration of these electrons follows from the principles of quantum mechanics. The chemical properties of the atom are determined by the number of protons, in fact, by number and arrangement of electrons. See also: Atomic Number – Does it conserve in a nuclear reaction? Atomic Number and Chemical PropertiesĮvery solid, liquid, gas, and plasma is composed of neutral or ionized atoms. It is the electrons that are responsible for the chemical bavavior of atoms, and which identify the various chemical elements. In a neutral atom there are as many electrons as protons moving about nucleus. The total electrical charge of the nucleus is therefore +Ze, where e (elementary charge) equals to 1,602 x 10 -19 coulombs. Total number of protons in the nucleus is called the atomic number of the atom and is given the symbol Z. The nucleus is composed of protons and neutrons. The atom consist of a small but massive nucleus surrounded by a cloud of rapidly moving electrons. Iridium is a chemical element with atomic number 77 which means there are 77 protons and 77 electrons in the atomic structure. K) 6.4 Thermal Conductivity 150 Specific Heat 0.13 Heat of Fusion 26.1 Heat of Vaporization 604 Atomic Number of Iridium.

Iridium – Properties Element Iridium Atomic Number 77 Symbol Ir Element Category Transition Metal Phase at STP Solid Atomic Mass 192.217 Density at STP 22.65 Electron Configuration 4f14 5d7 6s2 Possible Oxidation States +3,4 Electron Affinity 151 Electronegativity 2.2 1st Ionization Energy 9.1 Year of Discovery 1803 Discoverer Tennant, Smithson Thermal properties Melting Point 2410 Boiling Point 4130 Thermal Expansion µm/(m

Iridium 192