The answer to this would be helium
Answer:
Explanation:
Step 1. Identify the Group that contains X
We look at the consecutive ionization energies and hunt for a big jump between them
We see a big jump between n = 2 and n = 3. This indicates that X has two valence electrons.
We can easily remove two electrons, but the third electron requires much more energy. That electron must be in the stable, filled, inner core.
So, X is in Group 2 and P is in Group 15.
Step 2. Identify the Compound
X can lose two valence electrons to reach a stable octet, and P can do the same by gaining three electrons.
We must have 3 X atoms for every 2 P atoms.
The formula of the compound is 
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<u>Answer:</u> The given example is a physical change.
<u>Explanation:</u>
A chemical change is defined as the change in which chemical composition of a substance changes and results in the formation of a new substance. These are usually irreversible process.
A physical change is defined as the change in which only the shape and size of the substance changes and no new substance is formed. Only phase change occurs in these processes. These are usually considered as a reversible change.
For the given example: Moisture in the air forms beads of water on a cold window pane.
This is a physical change because water was initially present in the gaseous state (Moisture in the air) and when it is coming in contact with the cold window pane, the gaseous state of water gets converted into a liquid state.
Hence, the given example is a physical change.
Atoms are the smallest building block that can affect things, and are many many times smaller then cells. our eyes are not designed to see such small things
