Answer: The correct formula is 
Explanation:
For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here magnesium is having an oxidation state of +2 called as 
cation and bromine 
is an anion with oxidation state of -1. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral .
The cations and anions being oppositely charged attract each other through strong coloumbic forces and form an ionic bond.
Answer: Thus the correct option is D. All of the above describe a mole
Explanation:
According to avogadro's law, 1 mole of every substance weighs equal to molecular mass in grams.
1 mole of every substance contains avogadro's number 
of particles.
Mole is the S.I unit for measuring the amount of substance. It is often used to measure large number of particles.
Thus the correct option is D. All of the above describe a mole
Answer:
1.Ecologists often estimate the size and density of. populations using quadrats and the mark-recapture method.
2. The two key components of ecosystem stability are resilience and resistance.
3.The availability of abiotic factors (such as water, oxygen, and space) and biotic factors (such as food) affect population
4. When the climate is changing in the colder direction it effects the planet in the opposite way than it does when it is changing in the warmer direction. Ad nauseam the contemporary, it’ll keep getting hotter and at a greater rate so the ecosystem is going to die.
The half-life in months of a radioactive element that reduce to 5.00% of its initial mass in 500.0 years is approximately 1389 months
To solve this question, we'll begin by calculating the number of half-lives that has elapsed. This can be obtained as follow:
Amount remaining (N) = 5%
Original amount (N₀) = 100%
<h3>Number of half-lives (n) =?</h3>
N₀ × 2ⁿ = N
5 × 2ⁿ = 100
2ⁿ = 100/5
2ⁿ = 20
Take the log of both side
Log 2ⁿ = log 20
nlog 2 = log 20
Divide both side by log 2
n = log 20 / log 2
<h3>n = 4.32</h3>
Thus, 4.32 half-lives gas elapsed.
Finally, we shall determine the half-life of the element. This can be obtained as follow.
Number of half-lives (n) = 4.32
Time (t) = 500 years
<h3>Half-life (t½) =? </h3>
t½ = t / n
t½ = 500 / 4.32
t½ = 115.74 years
Multiply by 12 to express in months
t½ = 115.74 × 12
<h3>t½ ≈ 1389 months </h3>
Therefore, the half-life of the radioactive element in months is approximately 1389 months
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