*govern filling of orbitals by electrons The Aufbau principle is an expression of how electrons generally get added to an atom or a molecular system. It states that orbitals with lower energy are filled before those with higher energy. *Electrons enter orbitals of lowest energy first
*govern filling of orbitals by electrons when elements occupy orbitals of equal energy one electron enters each orbital until all the orbitals contain one electron with spins parallel.
Pauli exclusion principle
*govern filling of orbitals by electrons An atomic orbital contains a maximum of two electrons No more than two electrons can occupy an orbital, and this they can only do if they have opposite spin. (orbital filling diagram- only two per box)
Highest occupied energy level
It is the highest energy level (from the nucleus) that an electron occupies in an atom -where valence electrons are located
Inner shell electrons
These are the electrons that are not the valence electrons and are also known as core electrons. *electrons that are the closest to the nucleus
Octet of electrons
Elements like Helium, Neon, or Group 8a on periodic table, all have 8 valence electrons and are stable. -filled outer shell and stable atom.
Atom electron configuration
arrangement of electrons in an atom
Three methods used to represent arrangement of electrons
electron configuration (noble gas shortcut), orbital filling diagram, Lewis dot structure
Group Number and number of electrons in outer energy level
Group number in periodic table equals the number of valence electrons
S sub level
have spherical orbitals
p sub level
have dumbbell orbitals
d sub level
have clover leaf orbitals
As orbitals occupy higher energy levels...
the orbital size gets bigger (so that its area is further from the nucleus) the farther away it is the higher the energy
n2 Each orbital is assigned to a level and sublevel 1s= 1 orbital 2s= 1 orbital 2p= 3 orbitals 3s= 1 orbital 3p= 3 orbitals 3d= 5 orbitals 4s= 1 orbital 4p= 3 orbitals 4d= 5 orbitals 4f= 7 orbitals
atoms gain or lose electrons to achieve a filled outer energy level of electrons
Outermost principal energy levels Only s and p in highest energy levels Since total number of electrons possible in s and p sub levels is 8, there can be no more than 8 valence electrons.
Atoms with 3 or fewer valence electrons lose those electrons forming a positive ion, or cation
Atoms with 5 or more valence electrons gain electrons forming a negative ion, or anion.
Sub energy levels in Energy levels
1= s 2= s p 3= s p d 4= s p d f
why are outermost electrons only ones included in orbital filling diagram?
they are the only ones involved in chemical reactions and bonding. make it easier to decide what it could be bonded to and its characteristics, also its placement on periodic table.
What do the arrows on orbital filling diagram indicate?
The arrows represent the spin the electrons have. The pair of electrons spin in opposite directions, one clockwise and the other counterclockwise, and they repel each other.
Electron will spend about ___% of its time in ______
90% orbitals Describe orbitals using quantum numbers
How does a 2s orbital differ from a 1s orbital? how does a 2px orbital differ from a 2py orbital?
2s orbital is farther from the nucleus meaning it has more energy. (different level) 2px differs because they are on different axis and different places in space. (px, py pz) x axis, y axis, z axis, )
Periods in Period Table
Even though they skip some squares in between, all of the rows go left to right. When you look at a periodic table, each of the rows is considered to be a different period (Get it? Like PERIODic table.). In the periodic table, elements have something in common if they are in the same row. All of the elements in a period have the same number of atomic orbitals. Every element in the top row (the first period) has one orbital for its electrons. All of the elements in the second row (the second period) have two orbitals for their electrons. It goes down the periodic table like that. At this time, the maximum number of electron orbitals or electron shells for any element is seven.
Groups in Periodic Table
..and Your Groups Periodic Table showing Groups Now you know about periods. The periodic table has a special name for its columns, too. When a column goes from top to bottom, it's called a group. The elements in a group have the same number of electrons in their outer orbital. Every element in the first column (group one) has one electron in its outer shell. Every element on the second column (group two) has two electrons in the outer shell. As you keep counting the columns, you'll know how many electrons are in the outer shell. There are some exceptions to the order when you look at the transition elements, but you get the general idea.
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