What is a mole? How is the mole concept useful in chemical calculations?

Solution : Here, we need to find the number of protons, neutrons and electrons. We will use the definition of atomic number and mass number to find the numbers. Atomic number is the number of protons f ound in ucleus of an tom of that element. Atomic number is the unique identification of an element. In a neutral atom, number of proton is equal to the number o f electron. Hence, a tomic number indicates the number of protons and electrons in an atom of an element. Mass number is the sum of or total number of protons and neutrons found in the nucleu s of an tom of that lement. he mass number is different for each different i sotope of an e lement. Mass number is also unique identification of an element. Mass number is also helpful in finding the number of n eutrons in an at of an e lement. The d ifference between the mass number and the atomic number gives the number of neutrons. Now let’s find out the number of protons, electrons and neutrons. (a) Ar : Ar is the chemical symbol of Argon. The mass number of A is given : 40. The a tomic number of A is : 18. Atomic number gives the number of protons and the number of electrons. Therefore, Number of p rotons = 18. Number of electrons = 18. Number of neutrons is given by the difference of mass number and number of protons. Therefore, Number of neutrons = 40-18 = 22. 65 (b) Zn : Zn is the chemical symbol of Zinc. The mass number of Z n is given : 65. The a tomic number of Z n is : 30. Atomic number gives the number of protons and the number of electrons. Therefore, Number of p rotons = 30. Number of electrons = 30. Number of neutrons is given by the difference of mass number and number of protons. Therefore, Number of neutrons = 65-30 = 35. 70 (c) Ga : Ga is the chemical symbol of Gallium. The mass number of G a is given : 70. The a tomic number of G a is : 31. Atomic number gives the number of protons and the number of electrons. Therefore, Number of p rotons = 31. Number of electrons = 31. Number of neutrons is given by the difference of mass number and number of protons. Therefore, Number of neutrons = 70-31 = 39. (d) B : B is the chemical symbol of B oron. The mass number of B is given : 80. The a tomic number of B is : 5. Atomic number gives the number of protons and the number of electrons. Therefore, Number of p rotons = 5. Number of electrons = 5. Number of neutrons is given by the difference of mass number and number of protons. Therefore, Number of neutrons = 80-5 = 75. (e) W : W is the chemical symbol of Tungsten. The mass number of W is given : 184. The a tomic number of W is : 74. Atomic number gives the number of protons and the number of electrons. Therefore, Number of p rotons = 74. Number of electrons = 74. Number of neutrons is given by the difference of mass number and number of protons. Therefore, Number of n eutrons = 184-74 = 110. (f) Am : Am is the chemical symbol of Americium. The mass number of A is given : 243. The a tomic number of A is : 95. Atomic number gives the number of protons and the number of electrons. Therefore, Number of p rotons = 95. Number of electrons = 95. Number of neutrons is given by the difference of mass number and number of protons. Therefore, Number of n eutrons = 243-95 = 148.