atoms Flashcards
father of the atom
John Dalton
founder of electrons
- JJ Thompson
- created plum pudding
founder of nucleus and protons
Rutherford
founder of electron configuration
Bohr
founder of neutron
Chadwick
how are electrons held within the cloud surrounding the nucleus
held together by electrostatic forces of attraction between the positive nucleus and negative electrons
isotopes
elements with the same number of protons but different number of neutrons
isotopes have …
identical chemical properties (same electron config.) but different physical properties (mass, density, colour)
stable and unstable isotopes
stable: when there is a balance of attractive and repulsive forces in the nucleus
unstable: when these forces are unbalanced
- radioactive decay will occur as the nucleus is unstable
- releasing high energy particles or radiation
relative atomic mass formula
mass number = (percentage x a-mass) + (percentage x a-mass) / 100
the ability of atoms to form chemical bonds can be explained by …
- the arrangement of electrons in the atom and in particular by the stability of the valence electron shell
mass spectrometry
1) ionisation: high-energy electrons removes an electron from the atom giving them a +charge
2) acceleration: these +ions are accelerated through an electric field so that they are moving at high speed
3) deflection: ions are then deflected by a magnetic field according to their masses.
- Lighter ions are deflected more, the heavier they are: the less they are deflected
4) detection: detectors can measure the abundance of ions that strike them (giving qualitative data)
- this info can then be transferred to a mass spectrum
electron configuration
- electrons circled around the nucleus at fixed distances and only exist in certain energy levels
- electrons can jump from a low level to a high level when they gain energy (heat)
- electrons can drop from a high level to a low level when they lose energy (light)
- core electrons have low energy levels
- valence electrons have high energy levels
core charge
- measure of the attractive force felt by the valence electrons towards the nucleus
- inner shell electrons are said to be ‘shielding’ the valence electron from the full attraction of the nucleus
= #protons - #inner shell electrons
- across periods: increases
- down groups: remains constant
atomic radius
- distance from the nucleus to the valence-shell electron
- across periods: decreases (CC increase making them smaller)
- down groups: increase (higher energy levels are further away)
ionisation energy
- is the energy required to remove one electron from an atom of an element in it’s gaseous state
- 1st IE = 1st valence electron removed
- across periods: increases (CC increases requiring more energy to remove the electron)
- down groups: decrease (AR increases, electrons are further away)
electronegativity
- the ability of an atom to attract a pair of electrons in a covalent bond to its self
- across periods: increases (CC increases, incoming electrons will be attracted more strongly)
- down groups: decreases (AR increases, incoming electrons are not attracted as strongly)
metalloids
are located between metal & non-metals
bonds
metallic: metal with metal
ionic: metal with non-metal
covalent: non-metal with non-metal
element
a substance made up atoms with the same atomic number
compound
a pure substance made up of different types of atoms in a fixed ratio
mixture
different substances, not chemically joined with no fixed ratio
physical properties
properties can be determined without changing the chemical composition of the substance
chemical bonds …
can be explained by the arrangement of electrons in the atom
- in particular by the stability of the valence electron shell
ionic bonding can be modelled …
- as an arrangement of positively and negatively charged ions
- in a crystalline lattice with electrostatic forces of attraction between oppositely charged ions
metallic bonding can be modelled …
- as a an arrangement of atoms with electrostatic forces of attraction between the nuclei of these atoms and their delocalised electrons that are able to move within the 3D lattice
- delocalised electron gives the metal their typical physical properties
the metallic bonding model can be used to explain the properties of metals, including …
- malleability & ductile: ions are in layers and slippery over each other & still be attracted by the electron between them
- conductivity: heating cause fast movement of electrons, this motion associates with the lattice as it can be transmitted causing it to vibrate more strongly.
cation and anion
cation: + ion
anion: - ion
ionic bonds
the electrostatic force of attraction that exists between positively & negatively charged ions
why can’t ionic material conduct electricity
- when solid
- the ions are in fixed positions and can’t move
properties of ionic compounds
- hardness: strong force is required to break the strong electrostatic force of attraction between ions
- brittleness: forces between the particles are strong
- high melting point: high temps are required to overcome the electrostatic attraction so ions can move freely
- electrical conductivity: no free-moving charge particles are present
covalent bonding can be modelled as the
- sharing of pairs of electrons resulting in electrostatic forces of attraction between the shared electrons and the nuclei of adjacent atoms
properties of covalent network substances, include …
- high melting point
- hardness
- electrical conductivity
covalent networks
- solids are composed of atoms covalently bonded together into a 3D networks or layers of 2D networks.
elemental carbon exists …
- as allotropes: atoms in serval diff structural arrangements, giving different physical properties
- graphite, diamond and fullerenes
graphite properties that support model of CLL
- covalent layer lattice
- melting point: strong covalent bonds between atoms
- electrical conductivity: delocalised electrons are able to move freely
- weak dispersion forces: layers can slide over each other, reducing friction
diamond properties that support model of CNL
- covalent network lattice
- hard: strong covalent bonds between atoms
- high sublimation point: strong covalent bonds between atoms
- no electrical conductivity: no free-moving charge particles are present
nanomaterials
are substances that contain particles in the size range 1–100 nm
fullerenes
a molecule composed entirely of carbon
- form of a hollow sphere or tube
- each carbon atom is bonded to 3 other carbon atoms
nanomaterials uses
- waterproofing & tear-resistant fabrics
- strong, lightweight sport equipment
- wires, circuits & motors
the properties of covalent molecular substances, including …
- low melting and boiling point: bc of their structure and the weak intermolecular forces between molecules
intermolecular bonds (H20)
the force between H2 and O
intermolecular forces (H20)
the force between H2O and other H2O
intermolecular forces
the week forces between the molecules are responsible for the typical physical properties
successive ionisation energy
- after removing the 1st valence electron through ionisation, it is possible to remove the remaining electrons one by one
- more energy is required to ionise the valence electron as you get closer to the nucleus
covalent bonding rules
- first element stays the same
- second element change to ‘ide’
- add greek numbering to 1st & 2nd element
