Nuclear Composition

What are the Nuclear Composition?


An atom is the smallest unit of any matter which defines the physical and chemical properties of matters. Every matter is made up of neutral or ionized atoms. The atoms have very small size i.e. ~100pico-meter. Through the development of physics, atomic models have incorporated quantum principles to better explain and predict the behavior. This atomic structure was not fully understood until the discovery of the neutron in 1932. The history of the discovery of atomic structure is one of the most interesting and profound stories in science. In the year of 1911 Rutherford came to the conclusion that the atom had a dense nucleus through the Gold Foil Experiments. This theory would eliminate the idea that the atom was structured more like plum pudding. The plum pudding model was the leading model of atomic structure until Rutherford’s findings.

Nuclear Composition:

The atomic nucleus is the central part of the atom. It is composed of two kinds of subatomic particles, protons and neutrons. The number of protons and neutrons in the atom define what type of atom or element it is. An element is a bunch of atoms that all have the same type of atomic structure. For example hydrogen atom is made up of 1 proton, 0 neutrons, and 1 electron. So that the proton and the neutron is constituents of nucleus and electron revolves around the nucleus. The constituents of nucleus give the lots of information about the elements.

Nuclear Composition

The number of protons inside the nucleus gives us the atomic number. The protons have a positive charge. In order for the atom have a neutral charge, the electrons (-) need to balance it out. Therefore, in a neutral atom there are just as many protons as electrons. So, if you know the atomic number and know the charge of the atom then the number of electrons is easy to find; because the number of electrons equals the number of protons. If the number of electrons does not equal the number of protons in the nucleus then the atom is an ion:

Nuclear Composition

cation: number of electrons < number of protons

anion: number of electrons > number of protons

The nucleus contains essentially all of the mass of the atom. In order to discuss the mass of an atom we need to define a new unit of mass appropriate to that of an atom. This new unit of mass is called the “atomic mass unit” or amu. The atomic mass unit can be related to other units of mass using the conversion factor

1 amu = 1.67×10-24 gm

Since the atomic number gives us the number of protons in an atom and the atomic mass gives us the number of protons and neutrons, we can find the number of neutrons. To find the number of neutrons, just subtract the atomic number from the atomic mass.

Atomic mass – atomic number = number of neutrons.

Atomic mass = Number of protons + number of neutrons + number of electrons

The sum of the number of protons and neutrons for an atom is called its mass number and is given by the symbol A.

A = mass number = number of protons + number of neutrons

The symbolization of an atom is represented as

where Z= Atomic Number ( Number of Protons);  A = Mass Number ; X = Element symbol; A-Z = Number of neutrons

Nuclear Composition

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