Question

Please help!
1. How many valence electrons are in the outermost energy level of each of the following elements?
a. Helium
b. Lithium
c. Nitrogen
d. Magnesium
I listed them as letters to make it easier to understand...

Answer 1

Do you know how to write electronic configurations?

Answer 2

?electronic configurations?

Answer 3

Yes, like for helium (atomic number 2) we write \(\sf 1s^2\)

Answer 4

For nitrogen (atomic number 7) we write \(\sf 1s^2 2s^2 2p^3\)

Answer 5

any idea?

Answer 6

nope... no clue, sorry I am literally so stupid when it comes to all this electron atom stuff.

Answer 7

Then how will you solve this?

Answer 8

I am trying to understand it, so let me think out loud here

Answer 9

would you solve it like an equation? @Abhisar

Answer 10

Good, I may teach you a short trick but it may not be always correct but you will just do fine for school level.

Answer 11

ok... I will start with helium. 1s^2.
first would you find the square root of 1s?

Answer 12

No it's not square (-:
It means there are 2 electrons in 1s orbital.

Answer 13

ohhhk

Answer 14

Leave it, just remember the sequence 2, 8, 8, 18

Answer 15

Now, if i say you to write the configuration of nitrogen (atomic no 7).

You will write 2, 5 (Why five? because the sum has to be 7)

Answer 16

Getting?

Answer 17

ok I am following you

Answer 18

So, if i say write for lithium (atomic no. 3), how will ya do?

Answer 19

I would write 1, 2?

Answer 20

2, 1

Answer 21

Remember the series. It's 2, 8, 8, 18

Answer 22

ok?

Answer 23

ok I get it

Answer 24

For Magnesium (12)

Answer 25

8, 4?

Answer 26

Nopes.

Answer 27

6, 6

Answer 28

See the series, 2, 8, 8, 18

So will write first 2, now we need 10 more. So next we write 2, 8, now we need 2 more so finally we write 2, 8, 2. Got it now?

Answer 29

yehh

Answer 30

Finally write for hydrogen

Answer 31

sorry , for helium

Answer 32

attomic number is 2

Answer 33

wouldnt it just be 2?

Answer 34

Correct !!!

Answer 35

so I have the numbers:
a. Helium- 2
b. Lithium-2,1
c. Nitrogen-2,5
d. Magnesium-2,8,2

Answer 36

Well done!

Now we know that electronic configurations for the given elements are as following

a. Helium = 2
b. Lithium = 2, 1
c. Nitrogen = 2,5
d. Magnesium = 2,8,2


How to calculate valence electron now???

The last number in each of them represents the valence electrons. So for nitrogen, number of valence electrons will be 2.

Answer 37

huh?

Answer 38

Can you tell me the number of valence electrons for the rest?

Answer 39

if it's the last number, wait what is that referring to ?

Answer 40

what placement is it referring to?

Answer 41

I am not able to understand ur question..

Answer 42

what do you mean by "The last number in each of them represents the valence electrons."
^^^^^^^^^^^^

Answer 43

yes but you said that 2 was nitrogen's number, but wouldnt it be 5?

Answer 44

When did I say that?
Yes, nitrogen has 5 valence electrons.

Answer 45

XD "The last number in each of them represents the valence electrons. So for nitrogen, number of valence electrons will be 2."

Answer 46

Last is 5 :(

See, what we wrote for Nitrogen. (2, 5). 2 is first and 5 is last. Getting it?

Answer 47

Oh, sorry that was a typo :D

Answer 48

I see! so the numbers would be:
a. Helium = 2
b. Lithium = 1
c. Nitrogen = 5
d. Magnesium = 2

Answer 49

\(\color{blue}{\text{Originally Posted by}}\) @Abhisar
Well done!

Now we know that electronic configurations for the given elements are as following

a. Helium = 2
b. Lithium = 2, 1
c. Nitrogen = 2,5
d. Magnesium = 2,8,2


How to calculate valence electron now???

The last number in each of them represents the valence electrons. So for nitrogen, number of valence electrons will be 5.
\(\color{blue}{\text{End of Quote}}\)

Answer 50

Correct!

Answer 51

thank you

Answer 52

You're welcome (-: