Answer is: beryllium-10.
The diagram shows that atom has 4 protons, 5 neutrons and 2 valence electrons.
Atomic number is the number of protons, which is characteristic of a chemical element, beryllium (Be) is an element with atomic number 4.
Two valence electrons means that atom is from 2. group of periodic table, only beryllium is from that group; sodium (1. group), boron (13. group) and carbon (14. group).
Beryllium-10 has 6 neutrons, so it is isotope (different number of neutrons or mass number).
Answer: 4.9 + 3.822 = 8.7
Explanation: Hope this helps
a. 661.23 m/s
b. the rate of effusion of Ammonia = 4.5 faster than Silicon tetra bromide
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Further explanation
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Given
T = 25 + 273 = 298 K
Required
a. the gas speed
b. The rate of effusion comparison
Solution
a.
Average velocities of gases can be expressed as root-mean-square averages. (V rms)
R = gas constant, T = temperature, Mm = molar mass of the gas particles
From the question
R = 8,314 J / mol K
T = temperature
Mm = molar mass, kg / mol
Molar mass of Ammonia = 17 g/mol = 0.017 kg/mol
b. the effusion rates of two gases = the square root of the inverse of their molar masses:
M₁ = molar mass Ammonia NH₃= 17
M₂ = molar mass Silicon tetra bromide SiBr₄= 348
the rate of effusion of Ammonia = 4.5 faster than Silicon tetra bromide
