valence and core electrons
DESCRIPTION
Valence and Core Electrons. To find valence electrons , just look at the elements GROUP number Nitrogen is in group 17, so it has 7 valence electrons To find the core electrons total number of electrons– valence electrons 54 Xe 54 – 8 = 46 core 5 B 5 – 3 = 2 core. - PowerPoint PPT PresentationTRANSCRIPT
Valence and Core ElectronsTo find valence electrons, just look at the
elements GROUP number Nitrogen is in group 17, so it has 7 valence
electrons
To find the core electrons total number of electrons– valence electrons
54Xe 54 – 8 = 46 core5B 5 – 3 = 2 core
Quantum ModelWe already knew
that electrons were divided into shells. n = 1 (1st shell) n = 2 (2nd shell) n = 3 (3rd shell)
The quantum model breaks up each electron shell into subshells.
Quantum ModelThese subshells represent the area where
electrons are most probably located.
BECAUSE ELECTRONS TRAVEL IN WAVES, IT IS IMPOSSIBLE TO KNOW THE EXACT POSITION OF AN ELECTRON AT ANY GIVEN TIME.
Heisenberg Uncertainty Principle
Quantum Model Subshells
Each subshell has: A specific name A maximum capacity for electrons
Subshell Name Maximum Electrons
s 2p 6d 10f 14
Quantum ModelKEYs subshellsp subshellsd subshellsf subshells2 e-
2 e-6 e-
2 e-6 e-
10 e-
Electron Configurations
Shorthand notation to keep track of the electrons in an atom
Element Electron ConfigurationH 1s1
He 1s2
Li 1s22s1
Be 1s22s2
B 1s22s22p1
Electron Configurations Li: 1s22s1
Superscripts add up to total number of electrons for that atomEnergy
Level
electrons in each subshell
subshell
Electron Configurations
THE SEQUENCE IS THE SAME EACH TIME BECAUSE ELECTRONS MUST FILL UP THE LOWEST ENERGY LEVELS FIRST.
Aufbau PrincipleGerman for “building
up”
Energy Levels
Periodic Table and Electron Configurations
ElementElectron
ConfigurationH 1s1
He 1s2
Li 1s22s1
Be 1s22s2
B 1s22s22p1
C 1s22s22p2
N 1s22s22p3
O 1s22s22p4
Element
Configuration Element Configuration
F PAr KS SrN Ga
Quick CheckWhat is the lowest energy
level?
Which energy level is higher: 2p or 3s?
Which energy level is higher: 4s or 3d?
Noble Gas ShortcutElectron configurations get really long.To save time, we can use noble gases at the
end of each period to represent all the filled subshells before that spot on the table.
Element Electron Configuration
Be [He]2s2
Ca [Ar]4s2
Sr [Kr]5s2
Homework Q’sWrite shorthand electron configurations for:
1) nickel2) calcium3) strontium 4) magnesium5) barium6) titanium
7) 1s22s22p63s23p64s1
You Try Ita) Rbb) Brc) Csd) Bae) Snf) 1s22s22p63s23p64s23d1
g) 1s22s22p63s23p64s1