Published on March 10, 2014
PRESENTATION OUTLINE • History of atom • What is an atom? • Structure of atom • Nucleus of atom • Electrons • Protons • Neutrons • Thomson’s model of an atom • Rutherford’s model of an atom • Bohr’s model of an atom • What this particles consists of ? • Atomic structure • Isotopes • Isobars
HISTORY OF THE ATOM 460 BC Democritus develops the idea of atoms he pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called ATOMA
He suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them ATOM
Atom, tiny basic building block of matter. All the material on Earth is composed of various combinations of atoms. An atom consists of a cloud of electrons surrounding a small, dense nucleus of protons and neutrons. Atoms are the smallest particles of a chemical element that still exhibit all the chemical properties unique to that element. A row of 100 million atoms would be only about a centimetre long.
ATOMS MADE VISIBLE Individual atoms of the element silicon can be seen in this image obtained through the use of a scanning transmission electron microscope. The atoms in each pair are less than a ten-millionth of a millimeter (less than a hundred-millionth of an inch) apart.
Atoms are made of smaller particles, called electrons, protons, and neutrons. An atom consists of a cloud of electrons surrounding a small, dense nucleus of protons and neutrons. Electrons and protons have a property called electric charge, which affects the way they interact with each other and with other electrically charged particles
An atom consists of a cloud of electrons surrounding a small, dense nucleus of protons and neutrons. The nucleus contains nearly all of the mass of the atom, but it occupies only a tiny fraction of the space inside the atom. The diameter of a typical nucleus is only about 1 × 10-14 m (4 × 10-13 in), or about 1/100,000 of the diameter of the entire atom.
Electrons (e-) were discovered by sir. J.J. Thomson.Electrons are tiny, negatively charged particles around the nucleus of an atom. Each electron carries a single fundamental unit of negative electric charge–1.602 x 10-19 coulomb and has a mass of 9.109 x 10-31 kg. The electron is one of the lightest particles with a known mass. Electrons cannot be split into anything smaller, also electrons do not have any real size, but are instead true points in space-that is, an electron has a radius of zero.
Proton (p+) was discovered by E.Goldstein. Proton has 1 unit mass. Proton Protons have a positive electrical charge of 1.602 x 10-19 coulomb. This charge is equal but opposite to the negative charge of the electron. A proton’s mass is about 1,840 times the mass of an electron. Protons carry a positive charge of +1, exactly the opposite electric charge as electrons. The number of protons in the nucleus determines the total quantity of positive charge in the atom.
Neutron (n) was discovered by Sir James Chadwick. The neutron is slightly heavier than a proton and 1,838 times as heavy as the electron. Neutron, electrically neutral elementary particle that is part of the nucleus of the atom. The neutron is about 10-13 cm in diameter and weighs 1.6749 x 10-27 kg.
According to Sir Joseph model of an atom, it consists of a positively charged here and the electrons are embedded in it. The negative and the positive charges are equal in magnitude, as a result the atom is neutral. Thomson proposed that the atom of an atom to be similar to that of a Christmas pudding or a watermelon
An atom consists of a positively charged center in the atom called the nucleus. The mass of the atom is contributed mainly by the nucleus. The size of the nucleus is very small as compared to the size of the atom. The electrons revolve around the nucleus in well- defined orbits.
gold foil helium nuclei helium nuclei
Bohr agreed with almost all points as said by Rutherford except regarding the revolution of electrons for which he added that there are only certain orbits known as discrete orbits inside the atom in which electrons revolve around the nucleus. While revolving in its discrete orbits the electrons do not radiate energy.
electrons in orbits Nucleus
Water Molecule Hydrogen atom Hydrogen atom Oxygen atom
the number of protons in an atom the number of protons and neutrons in an atom 2 4 Atomic mass Atomic number Number Of Electrons = Number Of Protons
CONTD.... Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. • first shell a maximum of 2 electrons • second shell a maximum of 8 electrons • third shell a maximum of 8 electrons
Isotope, one of two or more species of atom having the same atomic number, hence constituting the same element, but differing in mass number. The nucleus, and mass number is the sum total of the protons plus the neutrons in the nucleus, isotopes of the same element differ from one another only in the number of neutrons in their nuclei.
The average mass of naturally occurring copper atoms is equal to the sum of the atomic mass for each isotope multiplied by its isotopic abundance. For copper, it would be (62.930 amu x 0.692) + (64.928 amu x 0.308) = 63.545 amu. The atomic weight of copper is therefore 63.545 g.
ISOBARS The total number of nucleons is the same in the atoms of this pair of elements. Atoms of different elements with different atomic numbers, which have the same mass number, are known as isobars.
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