Chemistry-4-Electron Sructure of Atom Student Note

Imran Syakir Mohamad Chemistry DACS 1233 1

Electronic Structure of Atoms

& The Periodic

Table Chapter 4


Quantum Numbers

Principal quantum number – ( n )

Angular momentum quantum number – ( l )

Magnetic quantum number – ( ml )

Spin quantum number – ( ms )


Quantum Numbers (n, l, ml, ms)

principal quantum number n

n = 1, 2, 3, 4, ….

n=1n=2

n=3

distance of e- from the nucleus


angular momentum quantum number l

for a given value of n, l = 0, 1, 2, 3, … n-1

n = 1, l = 0n = 2, l = 0 or 1n = 3, l = 0, 1, or 2

Shape of the “volume” of space that the e- occupies

l = 0 s orbitall = 1 p orbitall = 2 d orbitall = 3 f orbital

Quantum Numbers(n, l, ml, ms)


l = 0 (s orbitals)

l = 1 (p orbitals)


l = 2 (d orbitals)


magnetic quantum number ml

for a given value of l ml = -l, …., 0, …. +l

orientation of the orbital in space

for l = 0 (s orbital) ml = 0if l = 1 (p orbital), ml = -1, 0, or +1

if l = 2 (d orbital), ml = -2, -1, 0, +1, or +2



ml = -1 ml = 0 ml = 1

ml = -2 ml = -1 ml = 0 ml = 1 ml = 2


spin quantum number ms

ms = +½ or -½


ms = -½ms = +½

Experimental arrangement for demo the spinning motion of electrons


Existence (and energy) of electron in atom is described by its unique Quantum Numbers

Pauli exclusion principle

No two electrons in an atomcan have the same four quantum

numbers.




Shell – electrons with the same value of n

Subshell – electrons with the same values of n and l

Orbital – electrons with the same values of n, l, and ml

How many electrons can an orbital hold?


How many 2p orbitals are there in an atom?

How many electrons can be placed in the 3d subshell?


Electron configuration is how the electrons are distributed among the various atomic orbitals in an atom.

1s1

principal quantumnumber n

angular momentumquantum number l

number of electronsin the orbital or subshell

Orbital diagram

H1s1


Order of orbitals (filling) in multi-electron atom

1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s

“Fill up” electrons in lowest energy orbitals (Aufbau principle)


H 1 electron H 1s1

Li 3 electrons Li 1s22s1

B 5 electrons B 1s22s22p1

C 6 electrons C 1s22s22p2


The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins (Hund’s rule).

N 7 electrons N 1s22s22p3

O 8 electrons O 1s22s22p4

F 9 electrons F 1s22s22p5

Ne 10 electrons Ne 1s22s22p6


What is the electron configuration of Mg?

What are the possible quantum numbers for the last (outermost) electron in Cl?


Outermost subshell being filled with electrons


Paramagnetic

unpaired electrons

2p

Diamagnetic

all electrons paired

2p


When the Elements Were Discovered


ns1

ns2

ns

2n

p1

ns

2n

p2

ns

2n

p3

ns

2n

p4

ns

2n

p5

ns

2n

p6

d1

d5

d1

04f

5f

Ground State Electron Configurations of the Elements


Classification of the Elements


Electron Configurations of Cations and Anions

Na [Ne]3s1 Na+ [Ne]

Ca [Ar]4s2 Ca2+ [Ar]

Al [Ne]3s23p1 Al3+ [Ne]

Atoms lose electrons so that cation has a noble-gas outer electron configuration.

H 1s1 H- 1s2 or [He]

F 1s22s22p5 F- 1s22s22p6 or [Ne]

O 1s22s22p4 O2- 1s22s22p6 or [Ne]

N 1s22s22p3 N3- 1s22s22p6 or [Ne]

Atoms gain electrons so that anion has a noble-gas outer electron configuration.

Of Representative Elements


+1

+2

+3 -1-2-3

Cations and Anions Of Representative Elements


Ion charges


Na+: [Ne] Al3+: [Ne] F-: 1s22s22p6 or [Ne]

O2-: 1s22s22p6 or [Ne] N3-: 1s22s22p6 or [Ne]

Na+, Al3+, F-, O2-, and N3- are all isoelectronic with Ne

What neutral atom is isoelectronic with H- ?


Electron Configurations of Cations of Transition Metals

When a cation is formed from an atom of a transition metal, electrons are always removed first from the ns orbital and then from the (n – 1)d orbitals.

Fe: [Ar]4s23d6

Fe2+: [Ar]4s03d6 or [Ar]3d6

Fe3+: [Ar]4s03d5 or [Ar]3d5

Mn: [Ar]4s23d5

Mn2+: [Ar]4s03d5 or [Ar]3d5


Name the orbital described by the following quantum numbers :

a. n = 3, l = 0b. n = 3, l = 1c. n = 3, l = 2d. n = 5, l = 0

Q & A session


Give the n and l values for the following orbital a. 1s b. 3s c. 2p d. 4d e. 5f

What and the possible ml values for the following types of orbital? a. s b. p c. d d. f

Q & A session


How many possible orbital are there for n = a. 4 b. 10

How many electrons can inhabit all of the n = 4 orbital?

Place the following orbital in order of increasing energy: 1s, 3s, 4s, 6s, 3d, 4f, 3p, 7s, 5d, 5p

Q & A session


Write electron configurations for the following atoms: a. H

b. Li+

c. N

d. F-

e. Ca

Q & A session


Draw an orbital diagrams for atoms with the following electron configurations:

1s22s22p63s23p3

Q & A session

Chemistry-4-Electron Sructure of Atom Student Note

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