Answer:
The Aufbau Principle
Explanation:
In the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy level before occupying higher-energy levels.
Magic number is any number in electron shells that suggest stability. It corresponds to total number of electrons in filled electron shells.
If an electron is having magic number, then it forms stable bonds.
Explanation:
The magic numbers are 2,10,18,36,54, 86 and 126. This refers to the total number of electrons that an electron can have when it is completely filled.
Atomic nuclei which carries either of these nucleons have high binding energy as compared to others. Hence, they have high stability. Bonds in such elements are more strong.
Radioactive decay of such elements is very slow.
Eugene Winger coined the term "magic number".
A pure substance is a substance which cannot be separated physically or chemically. It is the same wherever found on earth. For example, pure gold is a pure substance. It will be the same whether it is found where you live or on another country. A mixture can be either homogeneous or heterogeneous. A homogeneous mixture is a mixture that looks the same throughout but is made of more than one element. An example of this would be salt and water mixture. A heterogeneous mixture is a mixture in which you can easily identify the different parts which make it up. An example of this would be pizza. Both these mixtures can be broken into different parts either physically or chemically.
Hope it helps :)
