Oxygen has an atomic number 8, because it has 8 protons and 8 electrons.
The first shell of an atom can hold up to 2 electrons but oxygen has 8 electrons, in that eight electrons 2 are in the first shell, so it has 6 more electrons left. The second shell can hold up to 8 electrons, oxygen has only 6 more electrons after the first shell is full, so it will have 6 electrons in the second shell
From this we know that oxygen has 2 shells so it is in period 2, and by counting from left to right, the sixth box in period 2 lies on group 16
Therefore Oxygen lies on group 16 and period 2
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Answer:

Explanation:
We have to take into account the expression for the position of the fringes

where m is the number of the maximum, d is the separation of the slits, D is the distance to the screen.
(a) By replacing we obtain

(b) more information is required to solve this point. Please complete the information.
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m = mass = 1,200 kg
A = acceleration = 3 m/s^2
Apply Newton's second law:
Force = mass x acceleration
F = 1,200 x 3 =3600 N
The net force the car experiences is 3600 N
The answer is Concave lenses