Biochemistry: Unit-1: Chemical Foundations of biology: Structure of atom. For S.R.T.M.U.Nanded, M.sc biotechnology CBCS pattern.

 Hello friends, In this article, I am trying to provide notes on the Biochemistry subject. So let's talk about Unit-1 i.e. chemical foundations of biology, from the reference book.

Structure of an Atom:

Atom: 'Each matter is composed of the very small particle' is called an atom. This atom can not be created, and can not be destroyed.

• Atoms of the same element are similar to one another and equal in weight.
• Atoms of different elements have different properties and weights.
• Atoms have 3 fundamental subatomic particle: Proton, neutron, and Electron

Regarding the arrangement of fundamental particles inside an atom. The first scientist Ernest Rutherford(1911) proposed the most satisfactory model which is accepted even today with some modifications. Accordingly, an atom is made up of a central nucleus. They contain positively-charged proton and neutral neutrons, surrounded by negatively-charged electrons. the electron is moving around the nucleus.

Orbit: In an atom, the discrete, successive, concentric volumes in space is known as Orbit or shells.

• The electron shells are numbered as 1,2,3,4,5,6 and 7 and are designated by the letters K,L,M,N,O,P,Q respectively. see image

Each shell has a certain number of electronand the maximum number of electron for each shell is fixed.the maximum number of electron is found from 2N square formula.where n is the serial number of the shell.Thus, the maximum number of electrons in K,L,M,N,O,P,Q shells will be 2,8,18,32,50,72,98 respectively. The maximum number of electrons in the outermost shell is 8 and in the penultimate(exceptional) shell is 18. 





 

 The shells are subdivided into subshells. The number of subshells in a shell is equal to the shell from within. so K shell has one subshell called s; second L shell has two subshells s and p; and third M shell has three subshells s,p and d ; and fourth subshell has four subshells s,p,d and f. the subshells s,p,d and f  can have a miximum of 2,6, 10 and 14 electrons, respectively.  

The position of electron in the various shells and subshells  are represented as follows. Major shells in which the electrons exist are indicated by the numbers 1,2,3 etc and the subshells designated by s,p,d,f etc. The superscript on s,p,d and f gives the number of electrons in subshells. Thus 1s2 indicate  the presence of two electrons in the s subshell of the first major shell(K). Similarly, 4f8 indicate the presence of 8 electrons in the f subshell of fourth major shell(N). 

 The mass of an atom depends entirely upon its nucleus. A neutron has nearly the same mass as a proton. In absolute terms, each proton or neutron weights 1.66043*10^-24g . The mass of an electron is negligible, about 1/1823 of the mass of a proton or neutron. 

 The mass of a proton or neutron is called the atomic mass unit(amu). 

 Atomic weight of an element may be defined as the combined weight of protons and neutrons, each taken as a unit weight. The number of protons on an atom is called the atomic number of the atom.  

Isotopes: The different atomic species, having the same atomic number, but different atomic weight is called as Isotopes.

This is all about the structure of atom