00:01Hi friends, education is the key to opening the door to new opportunities.
00:07An atom consists of an atomic nucleus and a number of electrons revolving around it.
00:15The same atom will have the same properties. Different atoms will have different properties.
00:23The image on this screen is an oxygen atom.
00:27The only problem here is how to express this atom so that it is easy to recognize without having to draw it.
00:36It is very troublesome if we always draw atoms like on a piece of paper.
00:43In general, we can express atoms with certain symbols.
00:49X is the symbol of an atom.
00:53In general, the symbol of an atom is an abbreviation of its name, O for oxygen.
01:02Z is the atomic number.
01:06This is the number of unit positive charges carried by the nucleus of an atom.
01:12Since the positive charge on the nucleus is due to the presence of protons in it,
01:18and each proton carries one unit positive charge.
01:22Therefore, the atomic number is numerically equal to the number of protons present in the nucleus of an atom.
01:31There are eight blue balls.
01:34That indicates eight units of protons.
01:37The value of Z is eight.
01:41Moreover, the number of protons in an atom is equal to the number of electrons since the atom on the whole is electrically neutral.
01:51Thus, the atomic number of an element is equal to the number of protons present in the nucleus or the number of electrons present outside the nucleus.
02:04Since the electrons are of negligible mass, the entire mass of the atom is due to protons and neutrons only.
02:19These particles are present in the nucleus and are collectively known as nucleons.
02:25The sum of the neutrons and protons is known as mass number.
02:32There are eight blue balls and eight pink balls.
02:37That represents eight units of protons and eight units of neutrons.
02:43The value of a is 16 because that is the number of protons and neutrons.
02:51Overall, we can write the oxygen atom with a symbol like this.
02:57When we find an atom with this symbol, we know that it is an oxygen atom.
03:03An oxygen atom has eight electrons, eight protons, and eight neutrons.
03:10Happy learning everyone!
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