Answer:
Gas turns into plasma when heat or energy is added to it. The atoms that make up the gas start to lose their electrons and become positively charged ions. The lost electrons are then able to float freely. This process is called ionization..
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The answer is HCl, C3H6 and C2H5OH. Hydrochloric acid has the lowest boiling point among the three choices since it only has weak dipole-dipole and Van der Waal's forces between molecules which are much weaker than the forces of attraction present in propane and ethanol. Ethanol has the highest since the hydrogen bonding present in ethanol make it hard to break the bonds.
The half-life of this radioisotope : 12 hr
<h3>Further explanation
</h3>
The atomic nucleus can experience decay into 2 particles or more due to the instability of its atomic nucleus.
Usually radioactive elements have an unstable atomic nucleus.
General formulas used in decay:

t = duration of decay
t 1/2 = half-life
N₀ = the number of initial radioactive atoms
Nt = the number of radioactive atoms left after decaying during T time
t=48 hr

The half-life :

I believe it's a pure element
Answer : A metal atom loses electrons from its outermost energy level and acquires a Positive Charge. These electrons join a nonmetal atom. The ionic compound formed because of this transfer of electrons is electrically Neutral.
Explanation :
All the elements try to acquire octet state by gaining or losing electrons. For metals, the number of valence electrons are less and it is easier to lose these electrons.
When electrons are lost, the number of protons become more than the electrons. This creates an excess of positive charge. As a result the species becomes positively charged and is known as cation.
During formation of ionic bond, metals always form a positive ion (cation) by losing electrons. These electrons are accepted by the nonmetals and they become negatively charged. A negatively charged ion is known as anion and nonmetals always form an anion.
These are attracted to each other due to the opposite charges present on them. In an ionic compound they balance the charges on each other making the compound neutral.
From the above discussion, we can fill in the blanks as follows.
A metal atom loses electrons from its outermost energy level and acquires a Positive Charge. These electrons join a nonmetal atom. The ionic compound formed because of this transfer of electrons is electrically Neutral.