elememts and the periodic table Flashcards
what is an atom
small particle of an element consisting of a nucleus with a positive charge
what is the Bohr Model
model of the atom where the nucleus contains the atomic number with positive charge and is surrounded by an equal number of electrons in orbital shells
what does ‘quantised’ mean
values limited to only specific values and not a continuous range of values
what is the quantum mechanical model
electrons constantly change positions (electron clouds)
orbitals
one orbital can hold a maximum of electrons but have different orbital ‘shelves’ that allow more electrons to be held in one orbital
the “electron hotel”
3rd floor - 9 rooms - 18 guests
2nd floor - 4 rooms - 2 guests
ground floor - nucleus
what is the Aufbau principle
the lowest energy configuration is obtained by putting electrons into the orbital with the lowest available energy first
Aufbsau principle explained
means the normal electronic structure of an atom is achieved by placing up to 2 electrons per box into the boxes in the sequence going from left to right
how to show an orbital holding helium
1s2
1 = energy level
s = type of orbital
2 = number of electrons in orbital
can be read as “one S two”
what is the Pauli exclusion principle
states that two electrons can have the same four quantum numbers
single orbital must have a maximum of 2 electrons that must have opposing spins or they would not have the same four quantum numbers
electron configuration examples
Hydrogen: 1 electron is n=1 (1s orbital) so configuration will be 1s1
Helium: 2 electrons so configuration will be 1s2
lithium: 3 electrons - the 1s orbital is full so there is no more orbitals for n=1 so we must move up to n=2 therefor configuration is 1s2 2s1
what are outer electrons that are involved in chemical bonding called?
valence electrons
