Answer: The correct option is 2.
Explanation: Polyatomic ions are defined as the ions in which two or more elements are covalently bonded to act as a single unit. They always carry some charge.
Examples of polyatomic ions are: 
known as hydroxide ion, 
known as sulfate ion
We are given a compound 
having 2 ions which are 
and 
. these ions are named as sodium ions and hydrogen carbonate ions.
Therefore, the correct option is 2.
It is a element.
Pure substances includes either compunds, or elements. Elements are the simplest form of pure substance, they only consist of one kind of atoms. On the other hand, compounds contains two or more elements that are chemically combined together. Although you couldn't separate a compound by physical methods like filtration, but you can seperate them with chemical methods such as heating or electrolysis, using electricity.
Therefore, since compounds can be broken down eventually, so, the answer will be element.
I think it’s solar but I’m sorry if that’s wrong :)
The order of increasing C-OC−O bond length is:
a < c < b < e < d
a < c < b < e < d
Therefore, the order of increasing bond strength is:
d < e < b < c < a
d< e < b < c < a
<h3>What is bond length?</h3>
The distance between the centers of two atoms that are covalently connected is known as the bond length. The number of bound electrons determines the bond's length (the bond order). The greater the attraction between the two atoms and the shorter the bond length are, the higher the bond order.
The average distance between the nuclei of two bound atoms in a molecule is referred to as bond length or bond distance in molecular geometry. It is a transferrable characteristic of a bond between atoms of fixed kinds that is comparatively independent from the other components of the molecule.
Bond length and bond order are related; the shorter the bond is when more electrons are involved in its production.
To learn more about bond length from the given link:
brainly.com/question/28225709
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