Which of the answer choices lists a true statement about ionic compounds? 1. they are formed by atoms that have the same number of valence electrons. 2. they are formed by ions that have the same charge. 3. they are formed by ions that have the opposite charges. 4. they are formed by atoms that have the same number of protons.

3. They are formed by ions that have the opposite charges.

Explanation:

Ionic compounds are formed when two oppositely charged ions react. Ionic bonds are formed when an atom has tendency to loose its valence electron/electrons and another atom has tendency to accept them. All the atoms on this earth want to be stable but they can be stable only when they have stable electronic configuration. Some atoms like noble gases have stable electronic configuration already so they don't need to react with any other atom of any other element but others do not have stable electronic configuration and in order to achieve this stable electronic configuration they need to react with atoms of other elements through various kind of bonds/interactions like ionic bond.

An example of ionic bond is interaction between magnesium ion (Mg2+) and chloride (Cl-) to form magnesium chloride (MgCl2).

Apart from ionic bonds there are other type of interactions too like covalent bonds, hydrogen bonds, hydrophobic interactions etc.

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.