Question

Atomic number of platinum is?
A. 68
B. 78
C. 74
D. 64

Answer 1

Hint: To find the atomic number of an element you should know about the no. of protons in an atom. If the no. of proton or electron is not given then you can use the periodic table to check the atomic number.
Atomic number = no. of proton = no. of electron

Complete step by step answer:
Atomic number of an element is defined as the number of protons in the nucleus of each atom of that element. Every element has a unique atomic number that identifies how many no. of protons are present in the atom. The atomic no. of an element can never change, because the number of the proton and electron in the nucleus of every atom of that element will always be the same. But the atomic no. of different elements will be different.
For an example in the nucleus of each oxygen atom the no. of protons remain 8 only and thus the atomic no. of oxygen is 8 but the atomic no. of carbon is 6 because it has only 6 protons in their nucleus.
Atomic number is represented as "Z".
As we know that atoms do not contain any net charge on it and thus they are electrically neutral. So, the no. of protons is equals to the no. of electron and therefore,
Atomic number (Z) = No. of protons = No. of electron
We can also find the atomic no. of elements by using the periodic table because in periodic table elements are arranged in very appropriate order. In the periodic table the elements are arranged in increasing order of their atomic number. Here, the atomic no. is displayed above the symbol of the element.
In the question we have to find the atomic no. and the symbol of platinum is represented as Pt. Here the no. of proton is not given so we will use the periodic table to check the atomic no.
So, if you will check the atomic number of platinum with its symbol (Pt) in the periodic table, you will find the atomic number as 78.
So, the correct answer is “Option B”.

Note: Platinum is the rarest element found in the earth crust. Platinum is highly stable and is used as a catalyst in many reactions. It is highly ductile and malleable. They are six isotopes of platinum. Atomic no. can be determined through its isotopes. The number of protons in platinum will also be 78.