periodic table Flashcards
what is an element
a substance that cannot be broken down into simpler substance by chemical means
who came up with an accurate defenition for an element
robert boyle
what did humphrey davey do
discovered potassium and other major elements by passing electricity through compounds containing those elements.
what is a triad
groups of three elements where the relative atomic mass of the middle one is the average of the other two.
what did johann dobereiner do
discovered the triads from a gradient in the relative molecular mass from chlorine to bromine to iodine
what are newlands octaves
arrangement of elements in which the first and eight element have similar properties
what did john newlands do
placed all the known elements at the time in order of atomic weight/r.a.m and noticed that the properties of the elements repeated with every eight element
why did newlands law of octaves not work out for all the elements
he didn’t take into account the fact that all the elements hadn’t been discovered and instead squeezed them all in together resulting in elements ending up in groups with no similar properties.
what is mendeleevs periodic law
if all elements are placed in order of increasing atomic weight properties will recur periodically
what changes did mendeleev make when he arranged the elements
he left gaps for the undiscovered elements
he put elements of similar properties in the same column
he switched certain elements placing them in groups with the same properties despite their atomic weight
what is the atomic number of an atom
the number of protons in the nucleus of an atom
what is the modern periodic table
arrangement of elements in order of increasing atomic number
what is the modern periodic law
when elements are arranged in order of increasing atomic number the properties recur periodically
what did henry mosely do
arranged the elements in order of atomic number which he discovered by studying the xray frequency of the atoms of elements emitted
what are the differences between the 2 tables
mendeleevs has spaces modern doesn’t
mendeleevs has 60 elements modern has over 100
mendeleevs put transition metals together modern has separate block for them
mendeleevs increases in atomic weight modern increase in atomic number
what is the mass number of an element
the sum of the protons and neutrons in an atom of an element
what is an isotope
atoms of the same element that have different masses due to the different number of neutrons in the nucleus
what is relative atomic mass
average mass of an isotope in an element
what are the 5 stages of mass spectrometry
vaporisation
ionisation
acceleration
separation into a magnetic field
detection
what is the prnciple of mass spectrometry
charged particles moving in a magnetic field are deflected according to their masses and are separated according to these masses
what is an electron configuration
arrangement of electrons in an atom of an element
what is the aufbau principle
when assigning the electron configuration of an atom in its ground state electrons must occupy the lowest energy levels
why is the 4s sublevel filled before 3d
it has less energy
why is the electron configuration of chromium and copper flipped
because a half filled or completely filled sublevel has extra stability
what is hunds rule of maximum multiplicity
when two or more orbitals of equal energy are available the electrons occupy them singly before doing so in pairs
what is paulis excursion principle
when filling the orbitals no more than two can fill each one and they must have opposite spins
