Elements and Atoms

Each and every substance in the world is made up of chemical elements.

An element is made up of very small particles that are not visible to the naked eye, these particles are atoms. Elements contain only one type of atom.

Elements are represented by their symbols in the periodic table. For example, carbon atom’s symbol is ‘C’.

Inside the Atom

Structure of the Atom

·       Atoms contain sub-atomic particles, which are proton, electron and neutron.

·       Proton and Neutron are situated inside the nucleus.

·       About 99 percent of mass is concentrated inside the nucleus of the atom.

·       Electrons revolve in the orbitals or shells that surround the nucleus.

·       Electrons carry negative charge = -1.6 * 10^-19 Coulomb.

·       Protons carry positive charge of the magnitude = +1.6 * 10^-19 Coulomb.

·       Neutrons are neutral particles.

·       Mass of Electron is about = 9.1093837 × 10^-31 Kg.

·       Mass of Proton is about = 1.67262192 × 10^-27 Kg.

·       Mass of Neutron is about = 1.674 x 10^-27 Kg.

·       Atomic Number is represented by Z and is equal to number of protons in an atom.

·       Mass Number is represented by A and is equal to sum of protons and neutrons in the atom.

·       Ions are formed by losing or gaining of electrons.

·       If an atom loses electron, a positive charge appears on the atom.

·       If an atom gains electron in its outermost shell, then a negative charge appears on the atom.

·       Atoms with the same number of protons but different numbers of neutrons are called isotopes. As a result, they have different masses but the same atomic number.

·       Although they have somewhat varied physical qualities, isotopes of the same element respond in the same way chemically because they have the same electrical configuration. ?

Models of the Atom

1.     Billiard Ball Model: Dalton proposed his atomic hypothesis based on all of his observations. It is usually called the "billiard ball model." Due to the lack of understanding of the atomic nucleus and electrons at the time, he described an atom as a ball-like structure.

2.     Plum Pudding Model: Thomson proposed in 1897 that the basic body of an atom is spherical in shape, with electrons (tiny particles within the atom that create a negative charge) and a positively charged "jelly" around the electrons that neutralises the electrons charge. Although Thomsons model did not accurately account for atomic structure, it served as the foundation for the development of other atomic models. This model is also known as plum pudding model of an atom.

3.     Rutherford’s Model: The positively charged particles and the majority of an atoms mass were said to be concentrated in a small volume according to Rutherfords Atomic Model. He called this area of the atoms the nucleus. Rutherfords nuclear model also proposed that an atoms nucleus be surrounded by negatively charged electrons. Rutherford also proposed that electrons travel at the speed of light around the nucleus. These elliptical paths were dubbed orbits by him.

4.     Bohr’ Model of an Atom: Niels Bohr, a Danish physicist, proposed the Bohrs Model in 1913. According to this model, electrons in an atom revolve around the nucleus in definite energy levels known as orbits/shells. According to the model, the maximum number of electrons that can be accommodated in any given orbit is 2n2, where n is the number of orbits. and the maximum number of electrons that can be accommodated in an atoms outermost shell is eight. Furthermore, the orbit closest to the nucleus has the least energy, while the orbit farthest from the nucleus has the most energy. By absorbing energy, electrons are excited to higher energy levels and return to lower energy levels by radiating energy.

5.     Current Model of an Atom: Electrons, neutrons, and protons make up the current model. The nucleus contains protons and neutrons, which are smaller quarks; electrons encircle the central nucleus.

Question: What experiment was conducted by Rutherford to propose his model of the atom?

Answer: Rutherfords gold foil experiment was set up as follows: A radioactive element that emitted alpha particles was directed toward a thin sheet of gold foil surrounded by a screen that allowed the deflected particles to be detected. To know more about the results of the experiment and what were the limitations of this experiment, visithttps://youtube.com/channel/UCoqI7C9rI2UbFPITF2bPgnQ.

Mass Spectrometry

Mass spectrometry is a type of molecular chemical analysis that makes it possible to ascertain the masses of certain molecules or isotopes. An unknown substance can be identified using mass spectrometry, and its relative abundance of each isotope of an element can also be calculated.