Chapter-18: Atomic Number and Nuclear Physics

Atomic and Nuclear Physics

The word atom is derived from the Greek word "otomos", meaning "indivisible". At one time, atoms were thought to be teh smallest particles of matter. Today we know that atoms are composite systems and contain even smaller particles: protons, neutrons and electrons. This unit: 

• describe the structure of an atom in terms of a nucleus and electrons. 
• describe the composition of the nucleus in terms of protons and neutrons. 
• explain the number of protons in a nucleus distinguishes one element from the other. 
• describe teh process of carbon dating to estimate the age of ancient objects. 
• describe hazards of radioactive materials. 
• show an awareness of the existence of background radiation and its sources. 

Short Question Answer
Q-1:	Define Atomic mass.
Ans:	It is equal to the number of nucleons in the nucleus.
Q-2:	Define blindness.
Ans:	Radiations are also source of blindness.
Q-3:	Define Deuterium.
Ans:	Deuterium contains one proton, one neutron and one electrons.
Q-4:	What is genetic mutation?
Ans:	Radiation cause genetic mutation in both human and plants. Some children are born with serious deformities due to genetic mutation.
Q-5:	What is an isotope?
Ans:	Isotopes are atoms of an element which has same number of protons but different number of neutrons in their nuclei.
Q-6:	What is Natural radioactivity?
Ans:	In natural radioactivity a naturally unstable element spontaneously emit radiation to be stable.
Q-7:	What is Leukemia?
Ans:	Radiation also cause the cancer of blood cells.
Q-8:	Difference between atomic number and atomic mass.
Ans:	Atomic number: 1. Atomic number is the number of neutrons present in nucleus. 2. It is represented by Z.
Q-9:	What is daughter nucleus?
Ans:	Daughter nucleus will be an isotope of helium.
Q-10:	Define protium?
Ans:	Protium contains one proton in the nucleus and one electron that resolved around the nucleus.
Q-11:	Write types of radiation.
Ans:	a. Alpha particles b. Beta particles c. Gamma particles.
Q-12:	What do you mean by unstable nucleus.
Ans:	The nucleus which emit radiations, all the time, and hence continuously change from one type of element to another are called unstable nucleus.
Q-13:	How half life can be calculated?
Ans:	Half life can be calculated by following formula. Remaining atoms = original atoms x 1/2t
Q-14:	Define Natural radioactivity.
Ans:	The spontaneous emission of radiation by unstable uncle is called natural radioactivity.
Q-15:	What is radioactive elements?
Ans:	The elements which emit radiations are called radioactive elements.
Q-16:	What is nature of cosmic rays?
Ans:	i. Proton ii. Electron iii. Alpha particles iv. Some larger nuclei
Q-17:	Give some safety measures to become safe from radiations.
Ans:	i. The sources should only be handled with tongs and forceps. ii. All radioactive sources should be stored in thick lead containers. iii. Never point a radioactive source towards a person.
Q-18:	Define Tritium?
Ans:	Tritium contains one proton, two neutrons and one electron.
Q-19:	Define alpha particle.
Ans:	Alpha particle has high mass due to this, its penetrating power is very short. It has large interacting and ionizing power. It is also the reason of its less penetrating power.
Q-20:	What is Gamma radiations?
Ans:	The gamma rays can penetrate to a considerable thickness of concrete. It is due to their large speed and neutral nature.
Q-21:	What is Beta particles?
Ans:	Beta radiation strongly interact with matter due to its charge and has a short range of penetrating as compared to gamma radiation.
Q-22:	What do you mean by stable nucleus?
Ans:	The nucleus which don’t emit radiations naturally are called stable nucleus.
Q-23:	Define cosmic radiation?
Ans:	The earth and all living thing on it receive radiation from outer space. This radiation is called comic radiations.
Q-24:	What do you mean by radioisotopes?
Ans:	Radioisotope: The stable and non-radioactive elements can also be changed into radioactive element by bombarding them with protons, neutrons or alpha particles, such artificially produced radioactive element are called radioactive isotopes,or radio isotope.