Fundamental Chemistry Flashcards
charges
neutrons- neutral
protons- positive
electrons- negative
elemental composition
top number= atomic number- protons
bottom number= atomic mass- protons + neutrons
isotope
element with the same number of protons and a different number of neutrons
changes atomic mass
same chemical characteristics
radioisotopes
isotopes that are radioactive
14C can be used to determine age of artefacts
measures decay of 14C using half life
isotopes- anti doping
differences in levels of metabolised testosterone can be measured
(listen to recording)
atom- electrons
electrons are found in orbitals
held in place by electrostatic attractions
electron shells fill sequentially
octet rule
confused - listen to recording
molecules
atoms are stable when their outer shell is full of electrons
atoms can gain (-ve) or lose (+ve) electrons to gain full outer shell
atoms can join with other atoms to form molecules known as bonding
chemical bonds
can be formed by sharing or transferring electrons
ionic- electron transfer
bond forms between metal and non metal eg NaCl
covalent - electron sharing
bond forms between non metals eg H2O
metallic- share a sea of delocalised electrons between metals
ionic bonding/ compounds- properties
high melting and boiling point- strong intermolecular forces (hard to break bonds)
soluble in water- highly polar
conduct electricity when in molten or aqueous solutions
brittle- form lattice structure
covalent bonding - properties
valency refers to the number of covalent bonds an atom can produce
low melting point and boiling point - weak intermolecular forces (volatile)
low solubility in water- low polarity
do not conduct electricity
can form double/ triple covalent bonds
metallic bonding
lattice made up of metal ions fixed in position
surrounded by sea of delocalised electrons
when voltage is applied, electrons move from high to low potential, forming current
conduct electricity due to free moving electrons
malleable (into sheets) and ductile (pulled into wires)
shapes of molecules
shape of molecule influences chemical behaviour
shape of covalent molecule depends on number of electron pairs in outer shell
electron pairs exist in a charge cloud
clouds repel eachother
polarisation
different atoms have different levels of electronegativity
more electronegative will attract shared electron pairs towards them
creates polar bond where electrongetaive atoms becomes -ve charge
atoms of similar electronegativity do not form polar bonds
electronegativity
measure of the ability of an atom that is bonded to another atom to attract electrons to itself
bond polarity
polarity can be shown by labelling the end of being partially +ve or partially -ve charged
non polar covalent= E<0.5 (eg ClCl)
polar covalent= >0.5 E < 2 (eg HCl)
ionic E>2 (eg NaCl)
polarisation importance
polar molecules are more soluble in water
steroid hormones are non polar and are not easily dissolved in blood/ urine
polarity determines its ability to transport in/ out of cells
intermolecular forces
between molecules (covalent is intramolecular, within molecule)
weaker than bonds between atoms
stronger IMF, more energy required to break molecules apart
gases- weak IMF
liquid/solid - strong IMF
london dispersion forces
atoms and molecules exhibit LDF between themselves
electrons orbiting nuclear create a cloud of neg charge
large molecules have large electron clouds + strong LD interactions
stronger LDF= higher boiling point
dipole dipole attractions
permanent dipoles eg HCl are in permanent state of polarisation + attract each other
eg HCl will attract HCl
eg hydrogen bonds (H covalently bonded to flourine, nitrogen or oxygen) are strong dipole dipole attraction
intermolecular forces- ionic
ionic compunds transfer electrons so atoms are permanently charged
attracts atoms togther and forms large lattices structures
bonds are very strong= high boiling point
in solution the atoms dissociate (separate) + remain in their individual charged atom state
ionic bonding
hydroxyl groups
oxygen bonded to hydrogen and organic molecule eg carbon
R group= carbon chains
polar bond between O and H and O and R
also called alcohols
-OH
amine groups
amine functional groups contain a nitrogen atom with a lone pair of electrons
class of amine depends what else it is bonded to
amino acid contain primary amine group- NH2 and R group
secondary amine= NH and 2 R group
tertiary amine= N and 3 R group
