Give two examples of each of the following: (a) alkali metals, (b) alkaline earth metals, (c) halogens, (d) noble gases, (e) chalcogens, (f ) transition metals.

Answer and Explanation:

(a) Alkali metals : The group 1 element in periodic table are known as alkali metals two examples are sodium (Na) , potassium (K)

(B) Alkaline earth metals : The group 2 elements are known as alkaline earth metals examples are  calcium (Ca), magnesium(Mg)

(c) Halogens : group 17th element are known as halogens examples are chlorine (Cl) , fluorine (F)

(D) Noble gases : the group 18th elements are known as noble gases examples are argon (Ar) ,Helium (He)

(E) Chalcogens  : The group 16th elements are known are chalcogens the examples are sulpher (S), oxygen (O)

(F) Transition metals : they are found in the middle of the periodic table examples are nickle (Ni) Copper (Cu)

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.