Answer:K2X
Explanation: Valency can be defined as the combining power of an element. It is the valency that dictates the value an element will have when writing a chemical formula for its compound.
MgX is a compound of magnesium and an element X. The valency of magnesium in most of its compound is +2. Now for the 2 to have been absent in the chemical formula, this shows that the element X itself have a valency if -2 for the valencies of both to have canceled out.
Now considering the element potassium, it is an alkaline metal belonging to group 1 of the periodic table. Hence, it is expected that it has a valency of +1
Forming a compound with element X means there would be an exchange of valencies between the two. We have established that x has a valency of -2. The formula of the compound thus formed by exchanging the valencies of both element would be K2X
Unlike humans, termites are able to extract energy from wood because: they have some microorganisms living in their gut that are able to break down cellulose.
Answer:

Explanation:
The Rydberg equation gives the wavelength λ for the transitions:

where
R= the Rydberg constant (1.0974 ×10⁷ m⁻¹) and

Data:

λ = 657 nm
Calculation:

1s2 2s2 2p6 3s2 3p6 4s1
s orbital can hold 2 electron
p orbitals can hold 6 electron
Explanation:
Entropy of a reaction ΔS∘rxn is the degree of disoderliness in a system. Gases generally have a higher degree of disorder compared to liquids. Hence for the reaction 2H2(g)+O2(g) ⟶ 2H2O(l), the entropy decreases sice the reactants are in the gaseous state and the products is in the liquid state of matter