Identify the parts of the atom that are labeled in the diagram

A- Nucleus

B-Energy levels

Explanation:

An atom refers to the smallest particle of an element that can take part in a chemical reaction.An atom is made up of two major parts namely; the nucleus and the energy shell or energy levels.The nucleus of an atom contains the sub atomic particles, protons and neutrons while the energy shells contain the sub atomic particle electrons.It is important to note that the protons in the nucleus are positively charged which makes the nucleus to be positively charged.On the other hand, energy shells are negatively charged because of the negative charge of the electrons.

42.9 h

Explanation:

From the question given above, the following data were obtained:

Original amount (N₀) = 100%

Amount remaining (N) = 25%

Time (t) = 85.8 h

Half-life (t½) =?

Next, we shall determine the number of half-lives that has elapse. This can be obtained as follow:

Original amount (N₀) = 100%

Amount remaining (N) = 25%

Number of half-lives (n) =?

N = 1/2ⁿ × N₀

25 = 1/2ⁿ × 100

Cross multiply

25 × 2ⁿ = 100

Divide both side by 25

2ⁿ = 100/25

2ⁿ = 4

Express 4 index form with 2 as the base

2ⁿ = 2²

n = 2

Thus, two half-lives has elapsed.

Finally, we shall determine the half-life of the of the isotope. This can be obtained as follow:

Time (t) = 85.8 h

Number of half-lives (n) = 2

Half-life (t½) =?

n = t / t½

2 = 85.8 / t½

Cross multiply

2 × t½ = 85.8

Divide both side by 2

t½ = 85.8 / 2

t½ = 42.9 h

Thus, the half-life of the of the isotope is 42.9 h