# Give the number of core electrons for F-?

##
A) 22

B) 75

C) 9

D) 4

E) 2

Please more detailed on how to get the answer. I'm really confused on this chapter of valance electrons and etc.

Thank you so much!!!

A) 22

B) 75

C) 9

D) 4

E) 2

Please more detailed on how to get the answer. I'm really confused on this chapter of valance electrons and etc.

Thank you so much!!!

##### 1 Answer

They include the

#overbrace(1s^2)^"core" " "overbrace(2s^2 2p^6)^("valence")#

I suppose I'll do a detailed review from particle properties all the way through quantum numbers and electron configurations.

**FLUORINE ELECTRONS**

*by definition*.

As a ** neutral** atom, the number of protons it has

**must be equal**to the number of electrons, as they are particles of opposite charge and a neutral atom has a total charge of zero.

Therefore, **both** the core and valence electrons, the latter being the ones used most often to react.

**FLUORINE ORBITALS AS RELATED TO QUANTUM NUMBERS**

An **atomic orbital** is given as the symbol

As ** 2nd** row of the periodic table, it has access

**up to**(and including) the atomic orbitals belonging to

**principal quantum number**

#n = 1, 2, 3, . . . #

defining each energy level. These are the *coefficients* of atomic orbital symbols.

For each energy level *shapes* given by **angular momentum quantum number**, where

#l = 0, 1, 2, . . . , n-1# .

Since the maximum **subshells** it has access to. As it turns out,

#l = 0 harr s# subshell

#l = 1 harr p# subshell

#l = 2 harr d# subshell

#l = 3 harr f# subshelland so on. This completes the

orbital symbolgiven by#nl# .

Therefore, fluorine atom contains electrons within

Furthermore, each subshell (**magnetic quantum number**:

#l = 0 harr m_l = 0#

#-># #1 xx s# orbital for any#n#

#l = 1 harr m_l = {-1,0,+1}#

#-># #3 xx p# orbitals for any#n#

#l = 2 harr m_l = {-2,-1,0,+1,+2}#

#-># #5 xx d# orbitals for any#n# etc.

This means we have one

**"PUTTING" ELECTRONS INTO ORBITALS**

Each of these orbitals (of a particular

By the **Pauli Exclusion Principle**, no two electrons can be in the same orbital and have the same spin value

Since two electrons in the same orbital have the same **spin quantum number** of

*As a result, each orbital can only contain two electrons, maximum.*

This then leads to the **electron configuration** of

#"F"^(-): " "1s^2 2s^2 2p^6#

where the superscripts denote how many electrons are in the subshell defined by

#nl# .

**CORE VS VALENCE ELECTRONS**

Since helium has two electrons, it is convenient to define the noble gas shorthand

We also call this thenoble gas corefor a reason! It contains the core electrons (most of the time)!

As such, it should at this point be straightforward that there are **core electrons** in **valence electrons**:

#color(blue)(overbrace(1s^2)^"core" " "overbrace(2s^2 2p^6)^("valence"))#