Activation energy is a thermodynamic barrier that must be overcome before products are formed in a reaction. It is the minimum amount of energy needed for a reaction to occur. The energy can be in the form of kinetic or potential energy. This concept was introduced by Svante Arrhenius, which brought about the Arrhenius equation which is a formula used to determine rate of reactions.
Answer:
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Atoms or molecule after gaining of electron possesses negative charge and is known as anion.
For the given sets:
The given elements are alkali metals and have tendency to lose electrons easily and form cations.
The given elements are non-metals and are electronegative. So, they gain electrons easily and form anion.
Carbon has tendency to form bond by sharing of electrons, Sulfur has tendency to gain electrons and form anion whereas Lead has tendency to lose electron.
Potassium and Iron has tendency to lose electron and form cation whereas Bromine has tendency to gain electron to form anion.
Hence, from the given sets, all elements of set: 
have tendency to form anions in binary ionic compounds.
Answer: Ioniç bond is also called electrovalent bond. It involves the transfer of electrons from positively charged ions to negatively charged ions. covalent bond is a type of chemical bond that involves electrons sharing by atoms of a molecule in order to achieve a stable electronic configuration.. Metallic bond is a type of chemical bond that forms between metal atoms and it occurs when positive metal ions are attracted to a negatively charged electron that are not associated with a single atom. The differences can be seen in the definitions above.
Pauli exclusion principle states that electrons which are identical cannot have the same quantum state.
