1 Atomic structure Flashcards
what is the charge,mass and location of a proton?
charge: +1
mass: 1
location: in nucleus
what is the charge,mass and location of an electron?
charge: -1
mass: 1/1840
location: around the nucleus in shells
what is the charge,mass and location of a neutron?
charge: 0
mass: 1
location: in nucleus
what is the name given to protons and neutrons?
nucleons
what force hold protons and neutrons together?
nuclear force
what force holds protons and electrons together?
electrostatic forces of attraction
what is an atomic number?
number of protons
what is the mass number?
number of protons +number of electrons
why is the mass of an atom made up of protons and neutrons and not electrons?
the nucleons make up most of the mass as electrons don’t weigh much and have little effect on mass of the atom
define isotopes
atoms with the same mumber of protons but different neutron number
explain why isotopes of the same element have identical propeties
they have the samer electronic configuration and the electronic configuration determines ther chemical propeties of an element
explain why we assume that there are the same number of protons and electrons in an atom
they have opposite charges of the same size and the atom is neutral
why do atoms of different isotopes of the same elementy vary in mass number
they have different number of neutrons in their nuclei
define relative atomic mass
average mass of an atom of an element on a scale where an atom of carbon-12 is 12
define realtive molecular mass
average mass of a molecule on a scale where an atom of carbon -12 is 12.
explain how a mass spectrometer works
ionisation: sample is vapourised. An electron gun is used to fire high energy electrons at it knocking one electrons off each particle becoming +1 ions
acceleration: positively charged ions are accelerated by electric field.all have the same KE.lighter ions end up moving faster than heavier ions
ion drift: ions enter region with no electric field.ions drift through it.lighter ions drift faster than heavier ions
Detection: lighter ions reach detector first before heavier ions as they are travelling faster.Detector detects charged particles and a mass spectrum is produced
what does a mass spectrum tell us
gives accurate information about relative isotopic mass and also about the relative abundance of isotopes.
Mass spectrometer can be used to identify elements.
and to determine relative molecular mass.
what is another name for shells
energy levels
how many electrons can be held in an orbital
1,2 no more
what are the different oribtals
S-orbitals
P-orbitals
D-orbitals
F-orbitals
how many orbitals does each type contain
S-one
P-three
D-five
F-seven
how many electrons can be held in each type of orbital
S-two
P-six
D-ten
F-fourteen
what is the shape of each type of orbital
S-spherical
P-Dumbell
what are the rules of orbital fillings
orbitals fill in order of increasing enrgy.Electrons pair with opposite spins.Orbitals with the same energy are occupied first
explain the rule of orbitals filling in order of increasing energy
1s is filled first
for n=2 shell,filling order is :2s,2p
for n=3 shell filling order is 3s,3p,3d
where odes the orbital filling rule cause confusion
the 3d sub-shell has higher energy than 4s.So the 4s fills before the 3d
expalain the rule of electron pairs with opposite spin
electrons are negatively charged and repel one another electrons have spin up or spin down
if electrons have opposite spin,the charge repulsion is counteracted eough for both to be in the orbital
explain the rule of orbitals with the same nergy are occupied singly first
within a sub shell,the orbitals have the same energy.One electron ocuupies each orbital before pairing begins.This prevents repulsion until no unocuppied orbitals remian
what ius the shell number reffered to as
principal quantum number
what happens in terms of energy sub-shells when forming ions
the highest energy sub-shells lose or gain electrons
where are the S block elements on the periodic table and what do they do and form in order to get an inert gas configuration
Thery are groups 1 and 2 and lose 1 or 2 electrons to form cations
where are the P block elements on the periodic table and what do they do and form in order to get an inert gas configuration
Thery are groups 5,6and 7 and they gain 1,2 or 3 electrons to form anions
where are the D block elements on the periodic table and what do they do and in order to get an inert gas configuration
they lose s and d electrons to form cations
why don’t group 0 need to lose,gain or share electrons
they have completely filled s and p shells and their full sub shells make them inert
chromium and copper dont fill their shells in the same way as other atoms.Explain the differences using electronic configuration
chromium donates one of its 4s electrons to the 3d sub shell because it prefers having a more stable half full d sub shell Cr(24 electrons):1S2 2S2 2P6 3S2 3P6 4S2 3D6
copper donates one of its 4s electrons to the 3d sub shell because it prefers having a more stable full d sub shell Cr(24 electrons):1S2 2S2 2P6 3S2 3P6 4S1 3D10
define ionisation energy
energy reqired to remove a mole of electrons from a mole of atoms in the gaseuous state
define 1st ionisation energy
energy required to remove one mole of electrons from one mole of gaseuos atoms
define 2nd ionisation energy
energy required to remove one mole of electron from each ion in 1 mole of gaseuos 1+ions
what is an equation for the nth successive ioniation energies
X^(n-1)+ —>X^n+ + e^-
explain how nucleaur charge affects ionisation energy and state how it changes across a period
nucleuar charge increases acroos a period :the more protons there are in the nucleus the more positively charged the nucleus is and the stronger the electrostatic force of attraction this decreases the atomic raduis because the electrons are being pulled inwards towards the nucleus so more energy is needed to remove thje outer electron so ioniation energy is high
explain how the distance between the outer electron and the nucleus affects ionisation energy and state how it changes down a group
distance increases down the group the more strongly attrac ted the elecron is to the nucleus the greater the electrostatics force of attrac tion between the outer elkectron and the nucleus is and so more energy is needed to remove the outer electron so ionisation energy is high
explain how sheilidng affects ionisation energy and state how it changes down a group
increases down the group.As number shells increases the electrostatic force attraction decreases this meaqns less energy is needed to remove the outer electron so ionisation energy is low
state and explain the general trend in ionsisation energy across a period
ionisation energy increases across a period although shielidng stays constant nucleuar charge(no. protons) increases this causes the atomic raduis to decrease across the period.The outer electron is more strongly attrcated to the nucelus and so the electrostatic force of attrcation increases therefore a lot of energy is needed to remove the outer electron
state and explain the general trend in ionsisation energydown a group
ionisation energy decreases because the increase in nucleuar charge is outwieghed by the increase in sheilding this increases the atomic raduis down the group the outer electron is furhter away from the nucelus and the electrostatyic force of attraction is decreasing so less energy is required to remove the electron
generally there is an increase in the 1st ionisation energy across a period.However,the energy decreases as you go from group 2 to group 3.Why?
the electron lost from group 3 is from the p orbital,while the one lost from group 2 is from the s orbital.The p orbital is higher nergyand better protected by shielding than the s orbital,so it requires less energy to remove
why do successive ionisation energies increase within each shell
electrons are being removed from an increasingly positive ion so theres less repulsion amongst the remaining electrons so they are held more strongly by the nucelsu
what do the big jumps show in successive ionisation energy graphs of an elemtn
shows a new shell is being broken into and shows and electron is being removed from a shell closer to the nucelsu
how do you work out the group number in succesive ionisation energies of an element graph
count how many electrons are being removed before the first big jump
how do you work out the electronic configuration of an element in its succesive ionisation energies graph
from right to left count how many points there are before each big jump to find out how many electrons are in each shell
explain why it is necessary to ionise molecules when measuring their mass in TOF spectrometer
ions,not molecules,will interact with and be accelerated by an electric field and only ions will create a current when hitting the detector
expalin why the second ionisation of boron is higher than the first ionisation energy of boron
the electron is being removed from a positive ion therefore needs more energy
explain why the ionisation energy of every element is endothermic
energy is required to overcome the attraction between the electron and the nucleus
explain how the detetctor in a mass spectrometer enables the abundance of an isotope to be meausred
the ions hit the detector and cause current the bigger the current the more of that isotope is proportional to abundance
explain how first and successive ionisation energies in
Period 3 (Na–Ar) and in Group 2 (Be–Ba) give evidence
for electron configuration in sub-shells and in shells.
there is a drop between groups 5 and 6.Phosphoros and sulfur atoms have identical shielding and the electron is being removed from a 3p orbital hwoever for phosphorous the electron is being removed from a singly-occupied 3p orbital whereases in sulfur the electron is being removed from a 3p orbital containing two electrons the repulsion between two electrons in an orbital means the electrons are easier to remove from the shared orbitals gving evidence for electronic strucutre
there is a drop between groups 2 and 3 aluminiums outer electron is in a 3p orbital rather than 3s the 3p orbital has slightly higher energy than the 3s orbital so the electron is to be found further form the nucleus .The 3p orbital has additional sheiling provided by the 3S2 electrons.Both of these factors are strong enough to overeide the effect ofd the increased nucleuar charge resulting in the ionisation nergy dropping.This pattern in ionisation energies provide evidence for the theory of electrons in sub shells.
