B) Mg is the alkaline earth metal w/12 protons so following the periodic table to the halogen in the same period is
Cl: Chlorine
C) The Neutral noble has w/ 18 electrons is argon so the metal in the same row is
Na: Sodium
Answer: c.They have a unique set of properties that can be used as identifiers.
Explanation:
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.
Compounds can be decomposed into simpler constituents using chemical reactions.
Example: Water 
Compounds have different properties than the elements it is made up of.
Thus the most accurate description of compounds is that they have a unique set of properties that can be used as identifiers.
4 total bonds if u have double,or triple then subtract from 4
Answer:
The internal energy(ΔE) of a substance is calculated below:
From the first law of thermodynamics;
ΔE=q+w
Explanation:
<u>ΔE=q+w</u>
here;
+q=endothermic reaction
-q=exothermic reaction
+w=work done on the system
-w=work done by the system
Given:
q=+1.62kJ=1620J
w=-874J
To solve:
the internal energy(ΔE)
We know:
ΔE=q+w
<em>according to the problem;</em>
ΔE=q-w
since;
w=-874J (i.e.)work is done by the system.
ΔE=1620-874
ΔE=+746J
Therefore the internal energy is +746J
i.e. the option is "c"(+746J)
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