electrons and bonding chp 5 Flashcards
what are shells
-shells are regarded as energy levels
-the energy increases as the shell number increases
-the shell number or energy level number is called the principal quantum number (n)
how many electrons are able to occupie the shell 1-4
what is the formula for calculating the number of electrons in each shell
2n^2
what is an atomic orbital
- a region around a nucleus that can hold up to 2 electrons
what make up the shells
shells are made up of sub shells which themselves are made up of atomic orbitals
each new shell gains a new type of sub shell and therefore orbital
what are the features of an s-orbital
-the shape of a sphere
-each shell from n=1 contains 1 s-orbital
-the greater the shell number (n), the greater the radius of its s-orbital
what are the features of a p-orbital
-the electron cloud is within the shape of a dumb-bell
-one orbital can contain 1 or 2 electrons
-there are 3 separate p-orbitals at right angles to one another (these orbitals are referred to as px,py and pz
-each shell from n=2 contains 3 p-orbitals
-the greater the shell number n, the further the p-orbital is from the nucleus
what are the features of the d and f orbtials
-each shell from n=3 contains 5 d-orbitals
-each shell from n=4 contains 7 f-orbitals
what is a sub-shell
- orbitals of the same type are grouped together as sub-shells to produce shells
table
how does the presence of sub-shells effect the number of electrons within a shell
how do orbtials fill
orbitals fill in order of increasing energy
why do electrons in the same orbitals spin oppositly to eachother
- helps to mitigate the repulsion between the like charges, within an orbital
How are orbitals of the same energy filled
-within a sub-shell, one electron occupies each orbital before pairing up starts, this prevents any repulsion between paired electrons until there is no further orbital available at the same energy level
what does the electron configuration show
shows how sub-shells are occupied by electrons
how would you write a shorthand configuration
the short hand is shown in terms of the previous noble gas plus the outer electron sub-shells of the element your illustrating
what do the blocks of the peridoic table tell us
s-block, highest energy electrons in the s-sub-shell
P-block, highest energy electrons found in the p-sub-shell
D-block, highest energy electrons in the d-sub-shell
how does ionisation effect the electron configuration
the highest energy sub-shells lose or gain electrons
whats unique about the 4s and 3d sub-shells
- 4s sub-shells fill and empty before filling and emptying of 3d sub-shelled
- as is at a lower energy level
what is ionic bonding
- electrostatic attraction between positive and negative ions
describe how to produce a dot and cross diagram for a ionic compound
- electrons from the oxidising atoms are shown as either cross or dots
- Show the outer shell of both ions with the electrons
- use square brackets to show charge is over whole ion
- show the charge of the ion just outside square brackets
what is the structure of an ionic compound and what causes this
ionic compounds form giant ionic lattices due to the fact that an ion attracts oppositely charged ions in all directions
what is the boiling and melting point of ionic lattices and how is it explained
-Almost all ionic compounds are solid and room temperature
-High temperatures are needed to provide the energy needed to overcome the electrostatic forces, therefore most ionic compounds have high melting and boiling points.
how does the individual charge of an ion effect the ionic compounds melitng and boling point
the melting points are higher for lattices containing ions with greater ionic charges, as there is stronger attraction between ions
Are ionic compounds soluble
many ionic compounds dissolve in polar solvents, such as water, by breaking down the lattice and surrounding each ion.
how does the charge of individual ions in the ionic compound effect the solubility of the ionic compound
in a compound made of ions with larger charges, the ionic attraction may be too strong for water to be able to break down the lattice structure and therefore the compound will not be very soluble
Are ionic compounds electrically conductive
in the solid state, an ionic compound does not conduct electricity, but once melted or dissolved in water the ionic compound does conduct electricity.
what explains an ionic compounds properties of electrical conductivity
- when solid no mobile charge carries to carry the charge, so not conductive
- once molten/dissolved, ions within compound no longer fixed, become mobile charge carries and can conduct electricity
what is a summary of the properties of ionic compounds
- high melting and boiling points
- dissolve in polar solvents
- conduct electricity when liquid or dissolved
- typically form ionic lattices
what is covalent bonding
covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
when does covalent bonding occur
- atoms in non-metallic elements (h2 & O2),
- compounds of non metallic elements (H2O & CO2)
- polyatomic ions (NH4+).
in which structures are covalent bonds found
a small covalent molecule (H2), a giant covalent structure (SiO2) or a charged polyatomic ion (NH4+)
what actually is a covalent bond
-A covalent bond is the overlap of atomic orbitals, each containing one electron, to give a shared pair of electrons
-The shared pair of electrons is attracted to the nuclei of both the bonding atoms
How is the charge distributed in a covalent bond
the attraction is localised, acting solely between the shared pair of electrons and the nuclei of the 2 bonded atoms.
Describe what a dot and cross diagram looks like for a covalent bond
use dots and crosses to show electrons so that we can determine the origin of each electron.
electrons are shared not transferred
what is a displayed formula
-a displayed formula shows the relative positing of atoms and the bond between them as lines
-paired electrons that are not shared are called lone pairs, these can also be added to a displayed formulae
how many covalent bonds can carbon, nitrogen, oxygen and hydrogen make
-carbon forms 4 bonds
-nitrogen forms 3 bonds
-oxygen forms 2 bonds
-hydrogen forms 1 bond
how do elements with access to a n=3 shell differ when bonding
the n=3 outer shell can hold 18 electrons, so more electrons are available for bonding, this can realist in different bonding arrangements for elements such as sulfur with 6 electrons in its outer shell
What is a dative covalent bond
A dative covalent bond is a covalent bond in which a shared pair of electrons has been supplied by only 1 of the bonding atoms.
what is an example of a molecule that contains a dative covalent bond
An ammonia ion contains a dative covalent bond
Name a compound/molecule that contains a triple covalent bond
triple covalent bonds form between nitrogen molecules in diatomic nitrogen molecules and between the carbon and nitrogen atoms in a molecules of hydrogen cyanide
Name a compound that contains a double covalent bond
double bonds exist between oxygen atoms within diatomic oxygen molecules and also between the carbon and oxygen in a carbon dioxide molecule
define average bond enthalpy
- average amount of energy required to break a particular type of covalent bond in a molecule
