foundations in chemistry Flashcards
how many electrons can the 1st-4th shells hold
1 - 2 electrons
2 - 8 electrons
3 - 18 electrons
4 - 32 electrons
electrons are located in shells at different energy levels, what kind of energy levels are shells closest to the nucleus at
the lowest energy level
what is an orbital
region of space that can hold up to 2 electrons
what determines which block of the periodic table an element is found in
which highest energy orbital is filled.
eg. if highest energy electron is found in a d-orbital, then element will be in d-block
what is an equation to work out the number of electrons in a shell
2 x n (the shell number) ^ 2
what is the bond angle of a molecule with a tetrahedral shape, what gives it it’s shape
109.5
4 bonding regions, no lone pairs, bonding pairs repel equally
what is the bond angle of a molecule with a pyramidal shape,
why does it have this shape
107
3 bonding regions, one lone pair, lone pair repel more strongly than bonding pairs
what is the bond angle of a molecule with a non linear shape, why does it have this shape
104.5
2 bonding regions, 2 lone pairs
lone pairs repel more strongly than bonding pairs
what is the bond angle of a molecule with a linear shape, why does it have this shape
180
1 bonding region
(sometimes 3 lone pairs)
lone pairs repel more strongly than bonding pairs
what is the bond angle of a molecule with a trigonal planar shape, why has it got this shape
120
3 bonding regions, no lone pairs, all bonding pairs repel equally
what is the bond angle of a molecule with an octahedral shape, why does it have this shape
90
6 bonding regions, no lone pairs, all bonding pairs repel equally.
what is the bond angle of a molecule with a square planar shape
90
what is electronegativity
the ability of an atom to attract the bonding electrons of a covelant bond towards it.
what can two atoms of differing electronegativity in a covelant bond end up as
a permanant dipole
(this is only if the dipoles are not symmetrically arranged, and so do not cancel each other out)
how can u test if a molecule is polar or non polar
polar molecules dissolve in polar solutions.
non polar molecules will not dissolve in polar solutions.
what would give a higher metling point, temporary dipole bonding or permanent dipole bonding
permenant dipole bonding
when does hydrogen bonding occur
if a H atom is directly attached to N, O or F
what are the two anomalous properties of water caused by hydrogen bonding
ice is less dense than water
higher boiling point and freezing point than would be expected
why is ice less dense than water
the strong hydrogen bonds in ice cause an open lattice to form in the solid state
why does water have a higher boiling point than expected
strong hydrogen bonds that require lots of energy to overcome
what are 2 factors that affect the strength of intermolecular forces
- number of electrons, high number of electrons, larger uneven distribution of electrons, stronger london forces.
- is molecule contains atoms of very different electronegativity, larger dipole meaning stronger permanent dipole-dipole interactions.
what are the rules for assigning oxidation numbers
- group 1 metals
- group 2 metals
- fluorine
- hydrogen
- oxygen
- chlorine
what is mean by atomic number
the number of protons in one atom of an element
what is meant by mass number
the number of particles present in the nucleus of one atom of an element (protons + neutrons)
what is meant by relative atomic mass
the weighted average mass of one atom of an element relative to 1/12th the mass of one atom of C12
define relative isotopic mass
the mass of one atom of an isotope relative to 1/12th the mass of one atom of carbon 12
what is meant by the term weighted average mass
the average mass taking into account the relative abundance of isotopes
what is the formula linking mass, volume and density
mass = volume x density
what is the difference between Ar and Mr
Ar - atomic mass of one atom of an element
Mr - average mass of a molecule, worked by adding all the Ar together.
what is meant by an isotope
atoms of the same element, with same number of protons, different number of neutrons.
when is relative formula mass used instead of relative molecular mass
when dealing with ionic compounds
define empiricle formula and molecular formula
empiricle formula - the simplest whole number ratio of each element in the compound
molecular formula - the actual number of atoms of each element in a molecule of a compound.
what is meant by avagadro’s constant
the amount of substance that contains as many particles as exactly 12 g of C12. number of particles is 6.02 x 10 ^ 23
if in a question see (RTP), what can we tell
one mole of molecules of any gas at room temperature pressure takes up 24 dm ^3
can use N = v/24
why is percentage yield not always 100
not all reactants react
side reactions occur
some is lost in the process of making.
why are isotopic masses and relative masses compared to C12
The mass of a C12 atom acts as the. standard for atomic masses.
how do u convert from mol dm ^-3 to g dm ^-3
multiply by Mr
what are the benefits for sustainability of developing chemical processes with a high atom economy
high % economy is less expensive, as less money and time is spent on separating the desired product from waste products.
high % economy means less waste products are produced
reactions are more sustainable because they use raw materials which are renewable and will never run out.
why do isotopoes have the same chemical properties
they have the same number of electrons in outer shell
DO NOT say ‘ same number of electrons ‘
