Chapter 5 - Electron Bonding & Structure Flashcards
shells are regarded as
energy levels
the energy increases as
shell no. increases
what is the principal quantum no.
the shell no. or energy level number
equation of number of electrons in a shell?
2 n (^2)
what is an atomic orbital?
a region around a nucleus that can hold up to 2 electrons, with opposite spins
an atomic orbital can hold a maximum of
2 electrons
4 different types of orbital are?
s,p,d,f
s orbital
- sharp
- the shape of a sphere
- each shell from n = 1 contains 1 s orbital
- the greater the shell no, the greater the radius of the s orbital
p orbital
- principal
-dumb-bell shaped - there are 3 seperate p orbitals at right angels to each other - p p p
x y z - each shell from n = 2 contains 3 p orbitals
- the greater the shell no., the further the p orbital from the nucleus
d orbitals, f orbitals
diffuse, fundamental
- each shell from n=3 contains 5 d orbitals
- each shell from n = 4 contains 7 f orbitals
what is a sub shell?
within a shell, orbitals of the same type are grouped together as sub-shells
filling of orbitals rule
orbitals fill in order of increasing energy
note: 3d is a higher energy level than the 4s subshell, so 4s fills first
electrons pair with _____ spins
opposite
what is the point of opposite spins?
the opposite spins help counteract the repulsion between the negative charges of the 2 electrons
name of model used to show the electrons
electrons-in-box model
shorthand electron configurations
elec congigs can be expressed more simply in terms of the previous noble gas plus the outer electron sub shells
when forming ions,
the highest energy subshells lose or gain electrons
4s subshell fills before the 3d subshell but it also
empties before the 3d subshell
the Heisenberg uncertainty principle states that?
it is impossible to certainly say where an electron is and where it will be going
each sub shell is composed of how many types of orbitals?
only 1
Aufbau principles?
- shells and subshells are filled according to a set no. of rules
how are electrons added?
1 by 1, the paired
Ar Equation
total of (% x mass no.)
special cases for electron config
Chromium (Cr) & Copper (Cu)
- electron moves from 4s orbital to 3d orbital reduces repulsion between electrons
What is an ionic bond?
strong Electrostatic attraction between positive and negative ions
Forming an ionic bond?
- between metal & non metal
- elements seek to gain a full outer shell of electrons
Dot and cross diagrams show the _______ __ __________?
Origin of electrons
Ionic structures?
- Exist in giant ionic lattices
- each ion is surrounded in all directions
- 3D lattice
Why do ionic substances have high melting and boiling points?
- solid at room temp e.g. salt NaCl
- because ionic bonds are strong electrostatic forces of attraction and so large amounys or energy are needed to break these bonds
What is a polar solvent?
A dolbeny which contains polar bonds
Ionic substances are soluble in?
Polar solvents e.g. water
Why do polar bonds occur?
- are a result if the unequal distrubution of sharing of electrons within a bond
- results in atoms having a slight charge
- these slightly charged atoms can attract the charged ions within ionic lattices
- the lattice becomes disrupted
Ionic substances - electrical conductivity?
They are electrolytes
When this happens the previously solid lattice breaks down and the ions are now free to move
- solid = ions fixed in place = no mobile chartge carriers
- liquid - lattice breaks down = ions free to move = mobile charge carriers
What is an electrolyte?
They can conduct electricity when melted or dissolved in water
Which 2 key factors determine the strength of an ionic bond?
- charge on the ions
- distance between the ions
Ions with greater charges will have ….
Greater electrostatic attractions between them and so form stronger bonds
Smaller ions…
- Have a smaller internuclear distance, meaning the electrostatic force of attraction is stronger
➡️ smaller ions firm stronger ionic bonds in more closely packed lattices
What is a covalent bond?
Strong electrostatic force of attraction between a shared pair of electrons and the nuclei of the bonded atoms
Covalent bonds….
Occur between 2 non metals - e.g Cl 2
Single covalent bond?
- involves ONE shared pair of electrons
- e.g. Cl 2, H 2 O
Multiple covalent bonding?
Involves more than 1 shared pair of electrons
- e.g. O 2 - 2 shared pairs, double bond
- e.g. - N 2 - 3 shared pairs - triple bond
Dative covalent bond?
- when both electrons in a bond are donated by the same atom.
- equivalent to other covalent bonds
- e.g NH 4
Simple molecular substances?
- Made up of small molecules
- in solid state, exist as a lattice
- simple molecules
- within each molecule, the atoms are tightly held together by covalent bonds
- weak intermolecular forces act betwern mols
Properties of simple molecular substances?
M.p, B.P
- Low - weak intermolecular forces of attraction between mols
- small amount of energy needed to disrupt thse forces
Simple molecular- solubility
- soluble in non polar solvents
- ‘like dissolves like’
- weak intermolecular forces between molecules of non polar solvent are similar to that in simple molecular substances, ➡️ these forces these forces are able to act between the molecules of simple molecular substance and the solvent
Simple molecular - conductivity
- non conductors
- no charged particles are free to move and carry charge
Giant covalent substances?
- atoms are joined to adjacent atoms by strong covalent bonds
- network of covalent bonds
- giant lattice is formed
- lots of covalsnt bonds throughout structure
- e.g. diamond, graphite, silicon dioxide
Giant covalent substances- M.P & B.P
- strong covalent bonds exist throughout lattice
- lots of enerhy required to break thse bonds
Giant covalent- solubility?
- insoluble in polar & non polar solvents
- strong covalent bonds are not disrupted by either type of solvent
Giant covalent - conductivity
- non conductors- no charged particles that are free to move and carry current
- EXCEPTION: GRAPHITE- between layers of the lattice, delocalised electrons r able to move , when voltage is applied these electrobs are free to move parallel to the layers
The shape of a compound or ion is dictated by?
- Number of electron pairs around the central atom
- the nature of these pairs- bonding or lone
Electron pair repulsion- bonding pairs
Pairs of electrons that are involved in bonding
These repel each other equally
Electron pair repulsion- lone pairs
- pairs of electrons that are not involved in bonding
- lone pairs repeal each other more than bonding pairs because thy are more elecrron dense
☆ each lone pair reduces the bond angle by about 2.5 °C
The Octet rule?
- through chemical bonding, elements usually achieve a noble gas configuration - a full outer shell
- Octet rule suggests 8 electrons in pairs will exist in the full outer shell where 4 electrons form full outer shells
Why is it not always possible to get 8 electrons in pairs in the outer shell?
There may be:
- too few electrons to form an octet
- more than enough electrons to form an octet
Not enough electrons- shrinking the octet?
- neither beryllium nor Boron have enough electrons to form an octet
- the unpaired electrons will pair up
- the element will not achieve an octet
Expanding the octet
- the bonding atom will have more than 8 electrons in its outer shell
- can occur in group 15- 17, from period 3 downwards
what is a covalent bond?
strong electrostatic force of attraction between a shared pair of electrons and the nuclei of the bonded atoms
diagrams for ionic bonding remember?
- don’t need to show transfers
- square brackets with charge
- valence shell electrons only
[ionic] the ions attract each other from all directions and form a ____ _____ ______
giant ionic lattice
metallic bonding definition?
metallic bonding is the strong electrostatic attraction between the cations and delocalised electrons
[metallic bonding] diagrams?
- metal ATOMS are close enough for outer shells to overlap and electrons can move throughout the outer shells of all atoms
- write charge on ion
- particles NEED to be TOUCHING
Why aren’t they metal ions?
electrons are delocalised, not lost so not an ion
covalent bonding definition: atom?
smallest particle that makes up an element that can show the element’s chemistry. Contains protons, neutrons, electrons
covalent bonding definition: electron?
a negatively charged subatomic particle with a relative mass of 1/1836 orbiting the nucleus in a shell.
covalent bonding definition: nucleus?
structure at the centre of the atom with an overall positive charge that contains protons & neutrons.
covalent bonding definition: : molecule?
a particle that has 2 or more non metal atoms bonded together covalent. Can be the same or different e.g. oxygen, CO2
covalent bonding definition: Ion?
an atom or group of atoms that has lost or gained electrons to have a + or - charge
covalent bonding definition: intermolecular forces
are BETWEEN molecules
- e.g. hydrogen bonds, permanent dipole forces or induced dipole forces
covalent bonding definition: intramolecular forces
are WITHIN a molecule i.e. covalent bond
dative covalent bonds involve?
ab lone pair of electrons and an empty orbital
how are dative covalent bonds shown?
➡
the average bond enthalpy is?
- the average energy needed to break 1 mole of covalent bonds forming gaseous atoms
s block ?
highest energy electrons in the s subshell
- left block of two groups
p block?
- highest energy electrons in the p subshell
- right block of 6 groups
d block?
- highest energy electrons in the d subshell
- centre blocks of 10 groups
why does 4s empty before 3d as well?
- energies of 4s and 3d subshells are very close together
- once filled, 3d energy level falls bellow 4s energy level
which ionic structures not be very soluble (in polar substances)?
- in a compound made of ions with large charges, the ionic attraction may be too strong for water to be able to break down the lattice structure.
solubility requires which 2 main processes?
- ionic lattice must be broken down - relative strngths of attractions within lattice
- water molecules must attract and surround the ions
summary of properties of ionic compounds?
- high MP &BP
- tend to dissolve in polar solvents such as H2O
- only coduct in liquid state or aqueous solution
a covalent bond is localised
acting solely between the shared pair of electrons and the nuclei of the 2 bonded atoms.
expansion of the octet is only possible from?
the n=3 shell, where a d subshell becomes available for expansion
dative covalent bond a.k,a
coordinate bond
in a dative covalent bond, the shared pair was orginally a ?
lone pair of electrons on one of teh bonded atoms
solubility of non polar simple molecular substances?
when in non polar solvent = intermolecular foces form between molecules & solvent
- the interactions weaken the IMF in the simple molecular lattice. the IMF break & compound dissolves
non polar simple molecular substance solubility in polar solvents?
- little interaction between molecules in lattice & solvent molecules
- inter molecular bonding within the polar solvent is too strong to be broken
solubility of polar simple molecular in polar solevents?
- may dissolve in polar solvents
- ## solubility depends on strength of dipole
melting points of individual metals depends on?
no. of delocalised electrons per atom
- metals with more delocalised electrons will have a higher MP
2 properties of metals?
- malleability - metals can be hammered into different shapes
- ductility - metals can be drawn out or stretched
