Answer: 1s²2s²2p³ or it can also be 3s²2p³
Answer:- 448 mL of hydrogen gas are formed.
Solution:- It asks to calculate the volume of hydrogen gas formed in milliliters at STP when 0.020 moles of magnesium reacts with excess HCl acid. The balanced equation is:

There is 1:1 mol ratio between Mg and hydrogen gas. So, the moles of hydrogen gas is also equals to the moles of Mg reacted.
moles of Hydrogen gas formed = 0.020 mol
At STP, volume of 1 mol of the gas is 22.4 L. We need to calculate the volume of 0.02 moles of hydrogen gas.

= 0.448 L
They want answer in mL. So, let's convert L to mL using the conversion formula, 1L = 1000mL

= 448 mL
So, 0.020 moles of magnesium would produce 448 mL of hydrogen gas at STP on reacting with excess of HCl acid.
Answer:
2. they eat plants that get their energy from the sun
Explanation:
Based on the way energy flows through an ecosystem, animals could not survive if they did not have the source of plants. So, the sun's renewable energy is important to animals because the sun helps them grow their food.
I hope this helps and makes sense!
I think the correct answers from the choices listed above are the second and the last options. Organic compounds are nonducting and insoluble in water because of the bonds that these compounds contain. Most organic compounds don't dissolve in water because they are nonpolar. They don't conduct electricity because they are covalent, not ionic.
Magnesium in hydrochloric acid forms H2 (hydrogen) gas according to the balanced chemical equation:
Mg + 2HCl→H2 + MgCl2