Answer:
C: 4
H: 1
Mg: 2
O : 6
Explanation:
You can quickly find out the number of valence electrons by looking at where the element is on the periodic table and referring to the table that is attached.
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The reaction that the graph represents is
A. Exothermic because Hrxn=-167 kJTo calculate Hrxn we apply the following equation:

Looking at the graph, and at the result of the calculations, we can see that the enthalpy of the products is
lower than the enthalpy of the reagents, because the sign is negative. That means that the reaction
releases energy in the form of heat and that the reaction is
exothermic.
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The new volume of the air bubble that has an initial volume of 5.0 ml released at the bottom of a lake where the pressure is 3.0 atm is 15mL.
<h3>How to calculate volume?</h3>
The volume of a given gas can be calculated by using the following formula:
P1V1 = P2V2
Where;
- P1 = initial pressure
- V1 = initial volume
- P2 = final pressure
- V2 = final volume
5 × 3 = 1 × V2
15 = V2
V2 = 15mL
Therefore, the new volume of the air bubble that has an initial volume of 5.0 ml released at the bottom of a lake where the pressure is 3.0 atm is 15mL.
Learn more about volume at: brainly.com/question/1578538
Answer:
Elements form compounds to satisfy the octet rule. Noble gasses never form compounds because they already satisfy the octet rule.
Explanation:
The octet Rule is the theory that an element will attempt to gain a valence of 8 by binding with another element in it's vicinity. This can happen in a variety of ways, but the main thing to remember is that they will take the "shortest path" to 8(I.e an element will sometimes lose an electron or 2 if it has a valence 1 or 2 to loop back around to 8, while an element with a valence of 6 or 7 will attempt to gain 2 or 1 electrons).
Valence of elements can be counted by group in the image attached.
Group 1 has a valence of 1, Group 2 has a valence of 2, then we move to group 13 which has a valence of 3, group 14 has a valence of 4, group 15 has a valence of 5, group 16 has 6, group 17 has 7, and group 18 is the noble gasses which have 8.