I think the family of Group 2 metals are most likely to form a 2+ion.
Hydrogen is the smallest chemical element because it consists of only one proton in its nucleus. Its symbol is H, and its atomic number is 1 .It has an average atomic weight of 1.0079 amu, making it the lightest element.
a.1.00784 u
b.Atomic-36
Kr
Krypton
Atomic Weight. 83.80
That means that there must be a balance between the positively charged protons and the negatively charged electrons. Atoms must have equal numbers of protons and electrons. In our example, an atom of krypton must contain 36 electrons since it contains 36 protons. Electrons are arranged around atoms in a special way.
Answer:
Reaction A, B, E and F are exothermic reactions.
Explanation:
Exothermic reactions are defined as the reactions in which energy of reactants is more than the energy of the products. In these reactions, energy is released by the system.
The total enthalpy of the reaction 
comes out to be negative.
Endothermic reactions are defined as the reactions in which energy of products is more than the energy of the reactants. In these reactions, energy is absorbed by the system.
The total enthalpy of the reaction comes out to be positive.
So, from the given option reaction which are exothermic are with negative value that enthalpy of reaction and those are:
1) 
,ΔH = -1203 kJ/mol
2)
,ΔH =-176 kJ/mol
3) 
,ΔH = -393.5 kJ/mol
4) 
,ΔH =-891 kJ/mol
Answer:
Radio waves are a type of electromagnetic radiation and they use it for communication for things like phones,computers, and just mobile devices.
An object in motion, will remain at a constant velocity unless an unbalanced force comes upon it and that is a proven fact.
