Atoms, Electrons And Bonding, Shapes Of Molecules (Module 2)✅ Flashcards
What are induced dipole dipole forces how are they formed
(London forces) they are present in all molecular substances, they occur because electrons are constantly moving around and there will be an uneven electron distribution, this causes a temporary dipole within a molecule
This temporary dipole induces a temporary dipole in a neighboring molecule there is then an attraction between them
What makes a stronger London force
The bigger the molecule the stronger the bonds as there are more electrons which means there are more London forces
When are there permanent dipole dipole attractions
Between polar molecules eg H-Cl molecules
Some molecules are non polar but contain polar bonds
What 3 atoms cause a hydrogen bond
N,O,F
How are hydrogen bonds formed
The polar bond between the H and N/O/F leaves the H nucleus exposed as H only has one electron.
• Therefore there is a strong attraction from the lone pair on the N/O/F of one molecule to the exposed H
nucleus of another molecule.
H is delta positive and N/O/F is delta negative
Give the list starting with strongest forces of attraction
Hydrogen bonds, permanent dipole dipole, London forces
When the structure type is monatomic what are the type of particles and which substances are they
Particles=atoms
Substances=group 0 elements
When the structure type is simple molecular what are the particles and which substances are they
Particles=molecules
Substances=most non metal expect group 0, most compounds made from non metals combined
When the structure type is giant covalent what are the particles and which substances are they
Particles=atoms
Substances=diamond, graphite,silicon, silicon dioxide
When the structure type is ionic what are the particles and what substances are they
Particles=ions
Substances=most compounds made from metals and non metals combined
When the structure type is metallic what are the particles and which substances are they
Particles=ions and delocalized electrons
Substances=metals
What is the atomic number
Number of protons and electrons if it’s not an ion
Goes below the mass number on the species eg 31P then it’s 15
15
What is the mass number
The top number
Is the number of protons and neutrons
How do you find the %abundance
%abundance=peak height/total heigh of all the peaks X100
How do you find the Mr using a mass spectrometer table
Mass number X %abundance and add up all the isotopes/100
Identify the species responsible for a peak at m/z 208
Pb 208+
82
How do you sketch what the mass spectrum of the element bromine of equal abundance would look like
158:1
160:2
162:1
81-81=152
81-79=160
79-81=160
79-79=158
Name the order of shells in electronic configuration
1s,2s,2p,3s,3p,4s,3d,4p
How many electrons can be held in each type of shell
S=2
P=6
D=10
What happens during mass spectrometer
Sample is vaporized and then ionized to form positive ions
Ions accelerated, heavier ions more difficult to reflect then lighter ones
Ions are detected on a mass spectrum as mass to charge ratio (m/z)
All ions are positive (+1)
What is the structure of S orbital
Spherical and contains 1 or 2 electrons
What is structure of D and F orbitals
D= same shape as p (dumbbell) but across 2 planes can take 10 electrons (daisy leaf)
F= same as D but across 4 planes can take 14 electrons
2 on each plane
Why do electrons fill up the sub shell with 1 electron first
Minimize repulsion and have the paired electron spin in a different direction to also minimize repulsion
What are the exceptions where 4s is not filled up first
Cooper and chromium
What electrons are lost first to form an ion
Highest energy electrons are lost first
4s is lost before 3d
For what type of bonding do you use square brackets for
Ionic
What happens to electrons during covalent, ionic and metallic bonding
Covalent=shared
Ionic=metal gives outer shell electrons
Metallic=atoms donate outer shell electrons to a shared pool
Do ionic compounds dissolve in polar substances
Most ionic compounds dissolve in polar substances like water
What elements in group 5,6,7 expand their octet
5:P As
6:S,Se,Te
7:Cl,Br,I,At
How much does a lone pair of electrons affect the bond angle by
-2.5 degrees
What is the equation to determine amount of electrons in a shell
2n^2
What metals have higher melting points
One with a greater charge and a smaller atom
How to convert degrees to kelvin
+273.
What is the ideal gas equation
PV=nRT
What are the unity’s for ideal gas equation
P=Pa
V=M^3
N=moles
R=8.31
T=kelvin
Describe linear shape of molecules
Example CO2,
Bond angle=180
Number of bonded pairs of electrons=2
Number of lone pairs=0
Describe bent shape of molecule
Example water
Bond angle=104.5
Diagram=2 straight lines below horizontal
Number of bonded pairs of electrons=2
Number of lone pairs of electrons=2
Describe trigonal planar
Example boron trifluoride
Diagram=3straight lines
Bond angle=120
Number of bonded pairs=3
Number of lone pairs=0
Describe tetrahedral
Example=methane
Diagram=2straight lines, 1 dash,1 wedge
Bond angle=109.5
Number of bonded pairs=4
Number of lone pairs=0
Describe pyramidal
Example ammonia
Diagram=1 straight line,1 wedge,1 dashed below horizontal
Number of bonded pairs=3
Number of lone pairs=1
Describe octahedral
Example sulfur hexafluoride
Diagram=2wedge,2 dash, 2 straight
Bond angle=90
Number of bonded pairs=6
Number of lone pairs=0
Describe trigonal bipyramidal
Bond angle:90 and 120
Tetrahedron shape
Describe trigonal pyramidal
Bond angle:107
Shape triangle
3 bonded pairs of electrons
1 lone pair of electrons
When does ionic compounds conduct electricity
When molten or in liquid state
What is the relative mass of a proton neutron and electron
P=1
N=1
E=1/1836
What is the definition of an isotope
atoms of the same element that contain the same number of protons and electrons but a different number of neutrons.
On an element eg 16O
8
Where is the mass number whag does it represent, where is the atomic number what does it represent, what happens in isotopes
Mass number =16, number of protons + neutrons
Atomic number=8, number of protons
In isotopes mass number increases bud atomic number stays the same
What is a positive ions called
What is a negative ion called
Cations is positive
Anions is negative
How many protons,neutrons and electrons are in 24 Mg2+ and 35 Cl-
12. 17
Mg= 12P, 12N, 10E
Cl=17P, 18N, 18E
What is relative isotopic mass
Mass of an isotope relative to 1/12 of the mass of an atom of carbon 12
What is relative atomic mass
Weighted mean mass of an atom of an element relative to one twelfth of the mass of an atom of carbon-12
How does a mass spectrometer work
- Sample placed in mass spectrometer
- Sample vaporized and then ionized to form positive ions
- Ions are accelerated. Heavier ions move more slowly and are more difficult to deflect than lighter ions, so the ions of each isotope are separated
- Ions are detected on a mass spectrum as a mass to charge ratio (m/z). Each ion reaching detector adds to the signal, so greater the abundance, the larger the signal
What is the equation for m/z
M/Z=relative mass of an ion/ relative charge of an ion
What is the principal quantum number
The shell number or energy level number
What is an atomic orbital
A region around the nucleus that can hold up to 2 electrons, with opposite spins
What is the structure of a p orbital, how many electrons can it take
Dumb-bell shape
Each shell contains 3 p orbitals
Why is 4S filled up before 3D
3D sub shell is at a higher energy level then 4S
How do you represent the spin of an electron in a shell
Arrows pointing different ways, 1 electron in each sub shell before there is 2
What do square brackets in dot and cross diagrams represent
The charge is spread over each ion and that the ions are separate entities
What are the 4 blocks on the periodic table and where are they
S= group 1,2 and helium
D= group between 2-3
P= 3-8
F= below the periodic table (not first column)
Draw the first and second ionization energy for helium
He=He+ +e- First
He+ = He2+. + e- Second
Include state symbols (g)
What does the large increase between the 7th and 8th ionization energy for fluorine suggest
8th electron must be removed from a different shell, closer to the nucleus and with less shielding (change from n=2 to n=1)
What do group 3 and 6 have a slight decrease in first ionization energy
Marks start of electron pairing in P orbitals of the p sub shell for 6th period
describe the development of the atomic models
1803=Dalton defined elements as atoms of same mass
1897=Thomson discovered electrons, development of plum pudding model
1911= Rutherford gold foil experiment, proposed idea of atomic nucleus
1913= Bohr developed nuclear model of atom
1926= Schrodinger discovered electrons can act as waves or particles
1932= chadwick discovered neutrons
why is there a general increase in first ionisation energy across a period
nuclear charge increases
shielding stays the same
nuclear force of attraction increases
atomic radius decreases
what does a giant metallic lattice allow a metal to do
conduct electricity and heat
give it high melting and boiling points
due to strong electrostatic attraction between cations and delocalised electrons requires a large amount of energy to overcome
what elements form solid giant covalent lattices, which ones conduct electricity and are they hard or soft
diamond=hard (lattice structure), doesn’t conduct
graphite=soft (layers slide over each other),conducts due to extra electron between layers
graphene=soft (layers), conducts
silicon dioxide=similar to diamond, high MP+BP, doesn’t conduct
what are the trends in melting points
increases from 1-4, drops very low from 5-8
1-4 higher due to giant structures
5-8 simple structures, size of van der waal forces determines MP+BP, those with more electrons have stronger intermolecular forces
