It can be determined by 2n^2 formula
where "n" is the no of shell:
1st shell = 2n^2 = 2(1)^2 = 2*1 = 2 electrons
2nd shell = 2n^2 = 2(2)^2 = 2*4 = 8 electrons
3rd shell = 2n^2 = 2(3)^2 = 2*9 = 18 electrons
4th shell = 2n^2 = 2(4)^2 = 2*16 = 32 electrons.
Answer:
Check the electronic configuration of elements.
Explanation:
▪Valence electrons are the elwctrons present in the outermost shell of any element.
For example,
Electronic Configuration of Sodium = 2,8,1
Here , Sodium has 1 valence electrons.
▪Valency of an element is the total no. of electrons to be gained/losed in order to achieve duplet/octate state.
For example,
Electronic configuration of Sodium = 2,8,1
Sodium can achieve octate state either by losing 1 electron or gaining 7 electrons. But losing 1 electron is eay than gaining 7 electrons. So Valency of Sodium = +1
☆Metals have 1 or 2 or 3 valence electrons.
☆Non metals have 4 or 5 or 6 or 7 valence electrons.
☆Noble gases tend to stay in duplet/octate state i.e they have 2 or 8 valence electrons.
Answer:
Work done = 600 J
Power used = 60 W
Explanation:
Given:
Force acting on the box is, 
Displacement of the box is, 
Time taken for the work, 
Now, we know that, work is said to be done by a force only when there is displacement caused by the force in its direction.
Here, the force acting on the box causes a displacement of 30 m in its direction. So, work done is equal to the product of force and displacement caused.
Therefore, work done on the box is given as:

Therefore, the work done is 600 J.
Now, we know that, power is given as work done per unit time.
So, power used is given as:

Therefore, the power used is 60 W.
Answer:
7.186
Explanation:
The mean is the average of some given data from a sample point.
To calculate the mean, we use the formula below:
Mean = ∑fx/∑f
Where f = frequency
x = sample data
From the given pH of the solutions, we can form a table:
x f fx
7.15 1 7.15
7.16 1 7.16
7.18 1 7.18
7.19 1 7.19
7.20 3 21.6
7.21 1 7.21
Now ∑fx = 7.15 +7.16 +7.18 + 7.19 + 7.20 + 7.21 = 57.49
∑f = 1 + 1 + 1 + 1 + 3 + 1 = 8
The mean =
= 7.18625 = 7.186
Frequency is represented by f in the formula v=fπ. Where π is wavelength , f is frequency and v is velocity. Frequency is the number of waves passing per unit time.