Answer: 
Explanation:
Alpha Decay: In this process, a heavier nuclei decays into lighter nuclei by releasing alpha particle. The mass number is reduced by 4 units and atomic number is reduced by 2 units.
General representation of an element is given as:
where,
Z represents Atomic number
A represents Mass number
X represents the symbol of an element
General representation of alpha decay :
The balanced nuclear equation when the isotope Strontium-90 decays by Q- decay is :

The concentration of a and b will decrease while c will increase provided all other physical quantities are kept constant in the reaction
Answer:
The major limitations of Newlands' law of octaves were : (i) It was applicable to only lighter elements having atomic masses upto 40 u, i.e., upto calcium. After calcium, the first and the eighth element did not have similar properties
109.5
tetrahedral shape:
number of electron pair = 4,
number of bonded pair = 4,
number of lone pair = 0.
These waxes are highly hydrophobic (repellant) of water, so the correct answer would be D) repel.
The wax coating put on the car creates a water repellant sheila that causes the water to bead up on the surface of the wax, rather than directly impacting the paint and surface of the body of the car. This prolongs the life and quality of the appearance of the car.