Answer:
Element with the smallest radius is Carbon.
Explanation:
In a periodic table, atomic radius increases down the group due to addition of a new shell and decreases across the period from left to right due to increasing nuclear charge.
Due to addition of more electrons in same shell and increase of positive charge in nucleus increases attractive forces between electrons and nucleus hence decreasing size.
Carbon and Lithium are present in same period and hence Carbon has smaller size; Potassium and Bromine are present in same period and hence out of the two, Bromine has smaller size.
On comparing Carbon and Bromine, atomic radius increases down the group hence, Carbon has the smallest radius among the four given elements.
The focal length of the mirror is 15 cm
From the question given above, the following data were obtained:
Object distance (u) = 30 cm
Image distance (v) = 30 cm
<h3>Focal length (f) =? </h3>
The focal length of the mirror can be obtained as follow:

<h3>Invert </h3><h3>f = 15 cm</h3>
Therefore, the focal length of the mirror is 15 cm
Learn more: brainly.com/question/1392083
Answer:
The wavelength of the light emitted by a hydrogen atom for the given transition is 2166 nm.
Explanation:
The energy of nth energy levels of the H atom is given as:

Energy of the seventh energy level = 


Energy of the seventh energy level = 


Energy of the light emitted will be equal to the energy difference of the both levels.


Wavelength corresponding to energy E can be calculated by using Planck's equation:


The wavelength of the light emitted by a hydrogen atom for the given transition is 2166 nm.
Answer:
6.44 moles
Explanation:
At STP, 1 mole = 22.4 L
145 L × (1 mole ÷22.4 L) = 6.44 moles