Answer:
Option C. The same number of energy levels.
Explanation:
From the diagram given above, element (i) belong to group 2 while element (ii) belong to group 6.
Also, both element i and ii belong to the same period (i.e period 4). This simply means that both element i and ii have the same number of energy levels.
NOTE: Elements in the same period have the same number of shells of electrons which simply means they have the same energy levels.
Answer:
1 g
Explanation:
The half-life of Am-242 (16 h) is the time it takes for half of it to disappear.
We can make a table of the mass left after each half-life.

The mass remaining after 48 h is 1 g.
Answer:
2Mg^+ +O2 right arrow 2MgO
Explanation:
Since Group 2 alkali earth metals have 2 valence electrons, they tend to lose those 2 when forming ionic bonds. And the Loss of Electrons = Oxidation (L.E.O. for short). Therefore this group, including Mg and Ca, have an oxidation of [+2].
So the correct answer is C) +2
Explanation:
1. Thermochemical equation is balance stoichiometric chemical equation written with the phases of the reactants and products in the brackets along with the enthalpy change of the reaction.
The given correct thermochemical reactions are:


2. Phase change affect the value of the enthalpy change of the thermochemical equation. This is because change in phase is accompanied by change in energy. For example:


In both reaction phase of water is changing with change in energy of enthalpy of reaction.