Atoms

Atom is the smallest particle of an element that has same chemical properties of that element. Everything in this universe including living things is made up of atoms.

Atomic Structure

A typical atom is composed of a nucleus in the center surrounded by a cloud of electrons orbiting the nucleus. The dense nucleus consists of subatomic particles called protons and neutrons. Nucleus is positively (+) charged and has the majority of the mass of an atom.

        By definition, atom has no overall electrical charge because equal number of negatively (-) charged electrons will neutralize the positively (+) charged protons. Thus, a typical atom will have equal number of protons and electrons.

STRUCTURE OF AN ATOM

Subatomic Particles

Proton: The proton is a subatomic particle that resides within the nucleus of an atom. The number of protons in the nucleus defines the atomic number of an element as outlined in the periodic table of elements. The proton has a positive electrical charge, equal and opposite to that of an electron charge. Number of protons in the atoms of a particular element is always the same, whereas the number of neutrons may vary. When these occur, the elements are called isotopes. The mass of a proton is approximately 1,836 times that of an electron.

Electron: An electron is a subatomic particle that orbits the nucleus of an atom. Negatively charged electrons form a cloud around the nucleus and attracted to the positively charged protons. The charge on an electron is equal and opposite of the positively charged proton. Electrons are very light particles and move at an appreciable fraction of light speed. The electron has a very small mass compared to proton. Mass of an electron is 2000 times lesser than the proton. Electrons orbit the nucleus in spherical shells of various radii, representing energy levels. The larger the spherical shell, the higher the energy contained in the electron.

Neutron: The neutron is a subatomic particle that resides within the nucleus of an atom. Neutrons are electrically neutral and carry no charge. The mass of the neutron is slightly larger than that of the proton.

Atomic Number

The number of protons in the element’s nucleus of an atom determines the atomic number. This is a unique identification number of an element that tells you how many protons are there in its atom. Since protons are equal to electrons, the atomic number is equal to the number of electrons as well. The atomic number of an element will never change. For example, all hydrogen atoms will have only 1 proton, whose atomic number is 1 and all carbon atoms will have only 6 protons, whose atomic number is always 6.

Atomic Mass

The total mass of protons, neutrons and electrons in a single atom when it is at rest is called atomic mass.

CARBON ATOM