In the early 1800s, the chemists were aware of only 30 elements, but with the development of nuclear physics, scientists are now able to identify more and more elements present on the earth. Based on the IUPAC standards, the current periodic table contains 118 elements. Among these elements, 92 are natural elements and the remaining … Read more
Symmetrical distribution of electrons allows half and completely filled subshells to become more stable. Two or more electrons with the same spin can exchange their position with the degenerate orbitals. The spinning of electrons introduces a new type of quantum mechanical interaction called Exchange energy, Eex. And, the exchange energy release is maximum in the … Read more
The atomic theory has evolved with the discovery of electrons, protons and neutrons and incorporated dual behavior of matter to propose a quantum mechanical model. An important section of this theory is the placement of electrons that surround the nucleus. Figure 1: Evolution of atom from Billard ball model (1804), Plum pudding model (1897), Rutherford … Read more
Orbitals in the same subshell are called degenerate orbitals and in these orbitals, electrons are filled in such a way that the pairing of electrons occurs only after each of the degenerate orbitals (same energy) occupies one electron. This is the Hund’s Rule of maximum multiplicity which also emphasize that the unpaired electrons present in … Read more
The concept of electronic configuration provides several attributes of an atom, such as the shape and energy of its orbitals that are responsible for characteristic properties of each element. It also provides an insight towards how chemical bonds are formed between atoms. This notation presents the energy levels, orbitals and the number of the electron … Read more
The atomic configuration can be defined by four quantum numbers (n, l, ml, ms) where ‘n’ is the principal quantum number, ‘l’ is the angular/orbital quantum number, ml is the magnetic quantum number and finally ‘ms’ is the electron spin quantum number. While ‘n’ denotes the number of electron shell i.e 1,2,3 and so on, … Read more
Compounds are made up of different elements and each has own chemical identity, so, the use of chemical formulas is considered as most succinct way to represent the elemental makeup. Empirical Formula It is formula which gives simples ratio of whole numbers of atoms in any given compound. It gives the composition of elements … Read more
Percentage Composition The percentage composition of any given compound is ratio of amount of every element to total amount of all elements present in compound. Then this value is multiplied by 100. This is mainly used to measure quantity in the terms of grams of elements which are present in solution. In general percentage composition … Read more
Elements An Element is defined as a material which cannot be changed or broken down into another substance using chemical means. It is a basic chemical building block of matter. It is made up of entirely from one type of atom. Atoms of the same element have the same atomic number or Z. For example, the hydrogen … Read more
Chemical bonding is an integral part of any chemical reaction between two different elements. Atoms combine to attain stability. Formation of bonds is certainly important for the combination to take place. There are several different types of bonds that include electrovalent or ionic bonds, coordinate bonds and covalent bonds. Each bond is known to have … Read more