atomic structure & periodic table Flashcards
define atomic number
the number of protons in the nucleus of an atom of that element
define mass number
the number of protons + number of neutrons
define isotopes
isotopes are atoms of the same element with the same number of protons but a different number of neutrons
(same number of electrons)
define relative atomic mass
the weighted mean mass of an atom of an element compared to the mass of 1/12th of a carbon 12 atom
define relative molecular mass
weighted mean mass of a molecule compared to the mass of 1/12th of a carbon 12 atom
define relative formula mass
the mean weighted mass of a formula unit compared to the mass of 1/12th of a carbon 12 atom
what is the relative mass and charge of a proton and where is it found
mass= 1
charge= +1
position= nucleus
what is the relative mass and charge of a neutron and where is it found
mass= 1
charge= 0
position= nucleus
what is the relative mass and charge of an electron and where is it found
mass= 1/1840
charge= -1
position= orbital
define ions
atoms that have gained or lost electrons and are represented with a charge (positive/negative)
what does a mass spectrometer do
measures the abundance of different isotopes
what are the five main stages of mass spectrometry
vaporisation
1) ionisation
2) acceleration
3) deflection
4) detection
what happens during ionisation in mass spectrometry
sample is vaporised, seperating the atoms or molecules. a stream of high energy electrons is fired at the sample, so the energy from these electrons strips electrons off atoms or molecules forming positive ions.
what happens during acceleration in mass spectrometry
the positive ions pass through an electric field which accelerates them into the instrument
what happens during deflection in mass spectrometry
the ions pass through a magnetic field and are deflected according to their mass and their charge
whats happens during detection in mass spectrometry
an ion detector at the end of the tube responds to ions of a particular mass/charge ratio and mass spectrum is produced
the relative abundance of each ion is recorded as a peak on the spectrum
what is the first ionisation energy
the energy required to remove one mole of electrons from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
what is an orbital
a region within an atom that can hold up to 2 electrons of opposite spins
what is a sub shell
a group of electrons in the same type of orbital within a shell (s, p, d or f)
what is periodicity
a regularly repeating pattern of physical, atomic and chemical properties within a period (with increasing atomic number)
what three factors affect 1st ionisation energy
the number of protons (nuclear charge)
the shielding
the atomic/ionic radius
does ionisation energy increase or decrease across a period
increases as:
-nuclear charge increases
-shielding stays roughly the same
-atomic radius decreases slightly
does ionisation energy increase or decrease down a group
decreases as:
-nuclear charge increases (outweighed)
-atomic radius increases
-shielding increases
how do flame tests work chemically
electrons in lower energy levels will gain energy and temporarily be excited into higher energy levels. when the electrons return to a lower energy state, discrete energies are emitted
what shape is an S orbital
spherical
what shape is a P orbital
dumbell
what order are the subshells filled in an atom
1s 2s 2p 3s 3p 4s 3d 4p 4d
when do you not fill the 4s subshell before the 3d subshell
with Cr (chromium) and Cu (copper)
in a period why does ionisation energy decrease from Be (beryllium) and B (boron)
2p electron is in a higher energy subshell than the 2s and so it is easier to remove the outer electron from B than Be
in a period why does ionisation energy decrease between N (nitrogen) and O (oxygen)
two electrons are paired in the 2p subshell of oxygen, all of the 2p electrons are unpaired in nitrogen. there is greater repulsion with the paired electrons in oxygen so it is easier to remove
what is the equation for Ar on a mass spec
m/z x abundance divided by total abundance
what is the equation for Ar on a mass spec
m/z x abundance divided by total abundance
what does atomic emission spectra provide evidence for
quantum shells
define relative isotopic mass
isotopic mass of an isotope relative to 1/12th of the mean mass of an atom of the carbon 12 isotope
define first ionisation energy
minimum energy required to remove 1mole of electrons from 1mole of atoms in the gaseous state
melting temperature across period pattern
Li + Be have metallic bonding - melting point increases due to greater charged ions
B + C form giant covalent lattices with strong covalent bonds, high melting point
N + O + F + N are all simple covalent held with weak London forces
what is bigger number on periodic table
mass number
what is relative isotopic mass
the mass of an atom of an isotope compared to 1/12th of the mass of a carbon 12 atom
what is successive ionisation energy
the remove of more than 1 electron from the same atom
