Question

Reading between the lines
1
In berylium, the first shell has 2 electrons, so
the second shell should also have 2 electrons.
So, the electronic configuration should be
(2, 2). Hence, the element is beryllium with
electronic configuration (2, 2).
29. Write down the electronic configuration of
the following elements from the given atomic
numbers. Answer the following question
with explanation.
[2 Marks each]
. 3Li, 14Si, 2He, 11Na, 15P
Which of these elements belong to period 3?
Ans:​

Answer 1

Answer:

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Explanation:

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Answer 2

Answer:

Elements Electronic configuration

Lithium. [ Li ] k = 2 , l = 1

Silicon. [ Si ] k = 2 , l = 8 ,m = 4

Helium. [ He ] k = 2 [ noble gas ]

Sodium. [Na] k = 2 , l = 8 , m = 1

phosphorus [P] k = 2 , l = 8 , m = 5

Fact :

The number of shells could be used determine the period number..

So,,

3rd period = silicon , sodium , phosphorus ,,,..