Answer:
is the isotopic notation of the atom
Explanation:
The isotope notation is:

<em>Where a is the mass number = Number of protons + Number of neutrons</em>
<em>b is atomic number = Number of protons</em>
The atomic number define the nature of the atom, the element with atomic number = 15 is phosphorus, P:

a = 15 protons + 16 neutrons = 31
b = 15
is the isotopic notation of the atom.
A reaction in which energy is absorbed from the surroundings is called anendothermic<span> reaction. In </span>endothermic<span> reactions the enthalpy of the products is greater than the enthalpy of the reactants. Because reactions release or absorb energy, they affect the temperature of their surroundings.
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<span>mass and velocity this is the answer im sure it is</span>
ωєℓℓ тнє ρнσѕρнσяι¢ α¢ι∂ мσℓє¢υℓєѕ αттα¢н тσ тнє мσℓє¢υℓєѕ σf тнє мιℓк, αи∂ тнαт ιи¢яєαѕєѕ тнє ∂єиѕιту αи∂ тнєи ѕєρєяαтєѕ тнєм fяσм тнє яєѕт σf тнє ℓιqυι∂ ιи ιт. тнє яємαιи∂єя σf тнє ℓιqυι∂ѕ,иσω нανιиg ℓєѕѕ ∂єиѕιту тнαи тнє ρнσѕρнσяι¢ α¢ι∂ѕ & тнє мιℓк мσℓє¢υℓєѕ, ѕσ ιт ιт иσω fℓσαтѕ σи тσρ.
нσρє ι ¢συℓ∂ нєℓρ уσυ.