It's called the periodic table because it arranges the elements the into repeating sets known as periods. this is defined by the <span>covalence of an element and the number of electrons i has in its outermost shell. I feel the the Best answer would be B. sorry if im wrong but i hope i helped :)</span>
Answer:
option a
Explanation:
Size of an atom (diameter) = 10⁻¹⁰ m
There are approximately 10²² atoms in a single drop of water. If they are put in a straight line, the length would be
l = diameter of an atom × number of atoms
l = 10²²× 10⁻¹⁰ m = 10¹² m
Distance between the Sun and the Earth is 1.47 × 10¹¹ m. The calculated length is greater than the distance between the Sun and the Earth.
Thus, option a is correct.
Any ride that oscillates back and forth or moves only in a complete circle utilizes periodic motion.
Answer:

Explanation:
It is given that,
Initially, the electron is in n = 7 energy level. When it relaxes to a lower energy level, emitting light of 397 nm. We need to find the value of n for the level to which the electron relaxed. It can be calculate using the formula as :


R = Rydberg constant, 

Solving above equation we get the value of final n is,

or

So, it will relax in the n = 2. Hence, this is the required solution.
True
The electromagnet will become stronger if we add more coils because there are more field lines in a loop then there is in a straight piece of wire. In a solenoid there are a lot of loops and they are concentrated in the middle, as more loops are added the field lines get larger, therefore making the electromagnet stronger.