The Atom Flashcards
What does the Mass number tell us about an isotope?
The number of protons and neutrons in the nucleus
What does the Atomic number tell us?
The number of protons in the nucleus
Where are protons and neutrons found?
In the nucleus
How would we calculate the number of neutrons in a isotope?
Mass number - Atomic number
Give the relative charge and relative mass of protons, neutrons and electrons
Proton- charge +1, mass 1
Neutrons- charge 0, mass 1
Electrons- charge -1, mass 1/1840
What did Ernest Rutherford discover?
Found that most of the mass and all of the positive charge was in a tiny central nucleus
What did Henri Becquerel discover?
Radioactivity, showing that particles come from inside the atom, therefore atoms are divisible
What did JJ Thompson discover?
The electron, and that is negatively charged, that all electrons from an atom are the same.
Suggested the precedes of protons to balance charge, suggested plum pudding model
What did John Dalton discover?
Suggested elements were made of invisible atoms,
Same elements = same mass
What did Robert Boyle discover?
Proposed there ewe substances that could be made simpler- chemical elements
electrons are arranged in energy levels and sub-levels, what letters are given to the sub-levels?
s,p,d,f
write an equation for the first ionisation energy of sodium?
Na(g) –> Na+(g) +e-
what is the electronic configuration for vanadium? (periodic table needed)
1s2, 2s2, 2p6, 3s2, 3p6,3d3, 4s2
which sub-shell fills first- 4s or 3d?
4s
what is the maximum number of electrons held in each of the s, p ,d sub-shells?
s-2
p-6
d-10
z for krypton is 36, what is the electronic configuration? (periodic table needed)
1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s2, 4p6
there are two isotopes of chlorine, Cl-35 (75%) and Cl-37 (25%), show that the R.A.M of chlorine is 35.5
(35 x 75) + (37 x 25)
____________________
100
=35.5
how do we work out the relative atomic mass of an element?
add up (mass x abundance) for each isotope and then divide by total abundance
(mass x Abundance
__________________
total abundance
what happens to first ionisation energies as we move left to right along the period? why?
it increases
because nuclear charge increases but shielding remains the same
what is an atomic orbital?
a volume f space that an electron (or pairs of electrons) fill
what is an energy level?
“a shelll”
a collection of electrons with similar energy. the first ‘shell’ contains 2, the second 8 and the third 18 electrons.
when moving right to left across the period 3, what exceptions are there for ionisation energy?
Auminium- because the electron is being moved from3p, which has a slightly higher energy level than 3s.
Sulfur- because there are two electrons in one of the 3p orbitals and so there is repulsion between them
what can we say about the spin of pairs of electrons?
paired electrons will have opposite spin
what is the rule for electron pairing in orbitals?
electrons will fill in singly within the same sub-shell, before they pair (because they repulse each other)
write the equation for the second and third ionisation energies of sodium
Na+(g) –> NA2+(g) + e-
NA2+(g) –> NA3+(g) +e-
define first ionisation energy
the energy required to remove one mole of electrons from one mole of atoms, in the gaseous state
how are electrons removed from atoms?
ioniation, the atoms are hit with a beam of electrons from an electron gun
what is an isotope
atoms of the same element, with the same number of protons and electrons, but a different number of netrons
what does letter A stand for?
mass number
what does the letter Z stand for?
atomic number
define second ionisation energy
the energy required to remove one mole of electrons from one mole of atoms, with one positive charge, in the gaseous state
when thinking about electrons what should we thnk
S- shielding A- attraction (to) N- necleus D- distance (of outer shell) E- elctrons
what does ionic bonding happen between
metal and non-metal
what properties do ionic compounds have
melting points
strong force between oppositely charged ions
molten when dissolved
what is covalent bonding
sharing pairs of electrons between atoms
what is another name for dative covalent bonding
co-ordinate bonding
what is dative covalent bonding
a covalent bond where both electrons in the bond have been contributed by one species
what happens in dative covalent bonding
an atom that is electron deficient, as it doesn’t have a full outer shell, the atom that is donating the electrons has a pair of electrons not being used, called a lone pair
what crystal structures conduct electricity? why?
al metallic, graphite
because they have delocalised electrons that are free to moe through the structure
what effect do pairs of electrons both bonding and non-bonding have on each other
they repel
what shape and bond angle would a molecule with only two bonding pairs of electrons in the outer shall have?
Linear
180’
what shape and bond angle would a molecule with only three bonding pairs of electrons in the outer shall have?
trigonal planar
120’
what shape and bond angle would a molecule with only four bonding pairs of electrons in the outer shall have?
tetrahedral
109.5’
what shape and bond angle would a molecule with only five bonding pairs of electrons in the outer shall have?
trigonal bipyramid
90’ and 120’
what shape and bond angle would a molecule with only six bonding pairs of electrons in the outer shall have?
octahedral
90’
what shape and bond angle would a molecule with three bonding pairs and one lone pair have?
triangular pyramid
107’
what shape and bond angle would a molecule with two bonding pairs and two lone pairs have
v-shape
104.5’
what shape and bond angle would a molecule with four bonding pairs and two lone pairs have
square planar
90’
what repels more, bonding pairs or lone pairs
lone pairs
what is ionic bonding
the electrostatic attraction between oppositely charged ions in a lattice
what is an ion
a charged particle
what charge do the ions of elements the groups 1,2,3,6,7 have?
1= +1 2= +2 3= +3 6= -2 7=-1
what is metallic bonding
attraction between delocalised electrons and positive ions, in a lattice
what is electro-negativity
the power of an atom to withdraw the electron density from a covalent bond
what is meant by a polar bond
where the charge in a molecule is not symmetrical, so one area is slightly more positive and another slightly more negative
what can we say about the polarity of bonds in elements
they are not polar
what can we say about the polarity of bonds between different elements
they will be polar to different extents depending on the elements
starting with the weakest, name the three types of intermolecular attraction
van der walls
permanent dipole-dipole
hydrogen bonding
what is a single covalent bond
a shared pair of electrons
what is a double covalent bond
two shared pairs of electrons
how does the strength of a covalent bond compare with the strength of a hydrogen bond
covalent bonds are stronger
what causes van der waals force
caused by instantaneous dipoles. these occur because in any instant electrons are not spread evenly and more will be in one area than another. this will, in that instant induce a dipole in its neighbour, leading attraction
where do we find van der waals forces and what affects its strength
found in all atoms and molecules. the more electrons present, the bigger the force
what causes permanent dipole- dipole force
attraction between molecules with permanent dipoles
what effects the strength of permanent dipole-dipole force
the bigger he difference in electro-negativity between a bonding pair, the greater the dipole and so the greater the force
what causes hydrogen bonding
when hydrogen is covalently bonded to NOF. the hydrogen can be shared between this and a lone pair on another molecule
why does temperature not increase while a substance is melting or boiling
he energy is absorbed as the bond weakens
what is the energy required to weaken the forces of attraction in a solid enough for a solid to turn into a liquid called
enthalpy change to fusion
what are the four types of crystal structure
ionic, metallic, giant covelent , molecular
what are ionic crystals held together by
intermolecular forces (van der waals, hydrogen, dipole-dipole) hold molecules together. covalent bonds hold atoms within the molecules together
what are metallic crystals held together by
attractions between positive metal ions and a negative ‘sea of delocalised electrons
what are giant covalent (macromolecular) crystals held together by
covalent bonds
what type of structure do the following crystals have? NaCl, Mg, Diamond, Graphite Iodine, Ice
NaCl- ionic Mg- metallic Diamond- Giant Covalent Graphite- Giant Covalent Iodine- Molecular Ice- molecular
what is electron repulsion theory
each pair of electrons around an atom will repel all other electron pairs
the pairs of electrons will take positions as far away from each other as possible
what does macromolecular mean
a macromolecular structure is one in which large numbers of atoms are linked in the regular three-dimensional arrangement by covalent bonds
why is the second ionisation energy of silicon is lower than the second ionisation energy of aluminium
Electron in Silicon is removed from a higher energy orbital/ more shielded
Predict the element in period 3 that has the highest second ionisation energy
Na
Electron is removed from 2p
explain why the ionisation energy of every element is endothermic
Energy needed to overcome attraction between electron and nucleus
Suggest why the electronegativity of the elements increase from lithium to fluorine
The attraction to the nucleus increases
The distance of the outer electron increases
But shielding stays the same
Explain how the current is generated in a mass spectrometer
Electrons transfer at the detector to the positive ion
Identify the period two element, from carbon to fluorine that has the largest atomic radius. Explain answer
Carbon > fewest protons > smallest nuclear charge > least attraction between protons and electrons > weakest nuclear attraction > similar shielding
State one reason why the first ionisation energy of rubidium is lower than the first ionisation energy of sodium
> Further from nucleus
from higher energy level
more shielding
Why is there no hydrogen bonding between phosphine molecules
There is not a great enough difference in electronegativity
In terms of structure and bonding, why does graphene have a high melting point
Covalent bonds are hard to break
Why can a meal be hammered into different shapes
The layers can slide over each other making it malleable
Suggest one reason why particles with the same mass and velocity can be deflected by different amounts in the same magnetic field
Different charges
