Answer:
Isotopes are basically atoms of an element that have an unequal number of neutrons and protons. Of course the proton number remains the same, but the neutron number either decreases or increases, which leads to an overall change in mass. However, no chemical properties of the atom/element are changed as the electrons are the same number and do not react. In regards to Helium 4, the original number of neutrons in Helium is 2, and protons 2 as well. We see an equal number of neutrons and protons, hence an unchanged mass, and the element is <em>not</em> an isotope.
During selection of indicator. We choose an indicator which have pH range equivalent to the pH change of reaction to give better result and better observation.
So there are some different indicator are used in table 2 as compared to the table 1.
- Alizarin and phenolphthalein are basic indicator and their pH range is more than 8 so they are used in table 2
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Lets take a moment to list all the characteristics of the group 18 (also known as noble gases and/or group 8) elements:
- They have 8 valence electrons.
- Don't need ANY more electrons because their octet is full (stable).
- Are stable
- Not reactive
- Known as the noble gases
Now.. lets take some time to think about why elements want to form ions:
Elements form ions to either gain or lose valence electrons to the element they bond with. This helps them GAIN a full octet. What is a full octet, you may ask? An octet is when an element has all 8 valence electrons and is stable, making it nonreactive.
Why would an element with a full octet want to bond? It already has a full octet, it does not need to bond.
That, my fellow Brainly user, is why the noble gases do not need to bond.
I really do hope this helps! Enjoy, and good luck on the studies.
Explanation:
As 
is a covalent compound because it is made up by the combination of two non-metal atoms. Atomic number of an iodine atom is 53 and it contains 7 valence electrons as it belongs to group 17 of the periodic table.
Therefore, sharing of electrons will take place when two iodine atoms chemically combine with each other leading to the formation of a covalent bonding.
Hence, weak forces like london dispersion forces will be present between a molecule of .
The weak intermolecular forces which can arise either between nucleus and electrons or between electron-electron are known as dispersion forces. These forces are also known as London dispersion forces and these are temporary in nature.
thus, we can conclude that london dispersion force is the major attractive force that exists among different molecules in the solid.
"n" represents principal energy level or principal quantum number. Principal energy levels are then subdivided into sublevels. The level of principal energy level is always equal to number of sublevels. Therefore if <span>principal energy level</span> = 4, then there are also 4 sublevels present, namely: 4s, 4p, 4d and 4f sublevels.
