Week 2 Flashcards
Melting
Solid to liquid
Freezing
Liquid to solid
Boiling/vaporising
Liquid to gas
Condensation
Gas to liquid
Sublimation
Solid to gas
Melting and billing points
Solid: mp-positive, bp- positive
Liquid: mp- negative, bp- positive
Gas: mp- negative, bp- negative
Electron configuration
Arrangement of the electrons around the nucleus
Shells
Electrons moved around the nucleus of an atom in specific energy levels
Ground state
When the electron is in the lowest possible energy shell
Transition
An electron could move from a lower energy level to a higher energy level by absorbing energy
State table
Solid: mp- positive Bp- positive Liquid: mp- negative Bp- positive Gas:mp- negative Be-negative
Excited state
High energy electron
Neils Bohr- the shell model
The visible hydrogen spectrum consists of four lines-red, green, blue and violet- observed by passing an electric current through hydrogen gas.
The electron will transition from its ground state to a higher state by absorbing energy.
The electron in the excited stage is unstable and so it falls back to the ground state and emits the absorbed energy. This energy corresponds to the coloured lines on the spectrum.
Shells
The major energy levels in which electrons are located
Shells are numbered 1,2,3 outwards from the nucleus in order of increasing energy
An electron that is close to the nucleus will be attracted more strongly to the nucleus than one that is further away.
Electrons in the same shell…
Are about the same distance from the nucleus (shell is circular)
Have about the same energy level (when the electron moves on the shell, no spectrum is observed)
The further an electron is from the nucleus…
The smaller the amount of energy required to remove it from the atom (because weaker electrostatic attraction)
Different shells
Hold different numbers of electrons
The octate rule
The outermost shell can never contain more than eight electrons regardless of the maximum possible number for that shell.
Shell no. To max. no. Electrons
2n^2
Valence electrons
The electrons in the outermost shell of an atom are called valence electrons and are involved in chemical reactions because they are unstable.
Sub-shells
Found within shells
The number of sub shells in each shell is equal to its shell number(shell 3 has 3 sub shells.)
Given the labels s,p,d,f
Have energies within each shell in the order s<p></p>
Pauli principle
Gives the number of electrons in any orbital
An atomic orbital can hold a maximum of two electrons.
Pauli principle table
Sub shell. No. Of orbitals. Max no of electrons
S. 1. 2
P. 3. 6
D. 5. 10
F. 7. 14
The order of filling the shells and sub shells
Electrons occupy the lowest energy sub shell in an atom first
As shells move away from the nucleus they get closer to each other. In some cases the sub shells of one shell are higher in energy than sub shells of the next shell (4s and 3D)
Sub shell energy formula
if n>_ 3; E(n+1)s
