<u>Answer: </u>The correct statement is X is the effective nuclear charge, and it increases across a period.
<u>Explanation:</u>
We are given that:
X = number of protons − number of core electrons
Effective nuclear charge is defined as the actual nuclear charge (Z = number of protons) minus the screening effect caused by the electrons present between nucleus and valence electrons. These electrons are the core electrons.
The formula used for the calculation of effective nuclear charge given by Slater is:
where,
= effective nuclear charge
Z = atomic number or actual nuclear charge or number of protons
= Screening constant
The effective nuclear charge increases as we go from left to right in a period because nuclear charge increases with no effective increase in screening constant.
Hence, the correct answer is X is the effective nuclear charge, and it increases across a period.
The unit 'mW' means milliwatts. It is a unit of work. There are 1,000 milliwatts in a 1 Watt of work. In 4 hours, there are 14,400 seconds.
Work= Energy/time
17 mW * 1 W/1000 mW = Energy/(14,400 seconds)
Solving for energy,
Energy = 244.8 J
Energy/photon = 244.8 J/(6.04×10²⁰) = 4.053×10⁻¹⁹ J/photon
Using the Planck's equation:
E = hc/λ
where h = 6.626×10⁻³⁴ m²·kg/s, c = 3,00,000,000 m/s and λ is the wavelength
4.053×10⁻¹⁹ J/photon = (6.626×10⁻³⁴ m²·kg/s)(3,00,000,000 m/s)/λ
λ = 4.9×10⁻⁷ m or 49 micrometers
The steam releases 39.9 kJ when it condenses..
The steam condenses and transfers its energy to the skin.
<em>q = m</em>Δ<em>H</em>_cond = 17.7 g × (-2257 J/1 g) = -39 900 kJ = -39.9 kJ
The negative sign shows that the steam is releasing energy
To know the density you also need to know the volume of the rock.
