Explanation:
The valency of the element is the measure of the combining power of the element with the other atoms when the element forms compounds or molecules.
<u>Thus, valency has to known to find the how the elements have been combined and how many electrons have been lost, gain or shared.</u>
Given that:
Element A has 3 valence electrons and element B has 2 valence electrons. To find the ionic compound, the valency of the cations and the anions are interchanged and are written in subscripts. Thus,
A B
3 2
Cross multiplying, we get the formula : 
<u>Hence, 3 is the subscript for Element B.</u>
The answer is the lake.
A lake is a large expanse of terrestrial water, consisting of streams that are linked to the lake. Although some dimensions of some salt-water lakes are considered island seas; they are therefore distinct from the lagoons, and are larger and deeper than the ponds, while remaining a water body by definition.
Dalton Found out there was a small, hard indestructible sphere that is the smalles part of an element.He created his own Atomic Theory:
-All Matter is made up of small particles called atoms.
-Atoms cannot be created, destroyed, or divided into smaller particles.
-All atoms of the same element are identical in mass and size. The atoms of one element are different in mass and size from the atoms of other elements.
<span>-Compounds are created when atoms of different elements link together in definite proportions.
</span><span>Rutherford had found the positively charged nucleus in the middle of every atom using his Gold Foil Experiment. While doing this experiment, he expected these particles to just pass right through the foil but they bounced right back. He also proposed there were negatively charged electrons revolving around the nucleus.
</span><span>Thompson found negative electrons and inferred atoms also contain negative particles. He inferred there was a lump of positively charged material, with negative electrons throughout. He used the Raisins Bun Model to explain.
</span>Chadwick <span>proved that it consisted of a neutral particle with about the same mass as a proton "Neutron" is the name given to the particle</span>
Bohr believed Rutherford's prediction was correct, but it wasn't complete. Bohr proposed electrons could only move between energy levels, rather then being able to move everywhere.
C is the correct answer since it outputs and inputs chemicals
For example, at atmospheric corrosion of copper:
2Cu + CO₂ + O₂ + H₂O = CuCO₃*Cu(OH)₂
and disolution of substances of copper in an acid condition:
CuCO₃*Cu(OH)₂(s) + 4HNO₃(aq) = 2Cu(NO₃)₂(aq) + CO₂(g) + 3H₂O(l)
CuCO₃*Cu(OH)₂(s) + 4H⁺ = 2Cu²⁺ + CO₂ + 3H₂O
