EL 3, 4, 5 Flashcards
when discussing electron shells, what is n
n = shell number
for the 1st shell, n=1
how many electrons can fit in each of the first to seventh electron shells n=1-7
- n= 1 2 electrons
- n= 2,3 8 electrons
- n= 4,5 16 electrons
- n= 6,7 32 electrons
what are the names of the different electron subshells and how many orbitals do each of them contain
- s,p,d,f
- 1 s-orbital
- 3 p-orbitals
- 5 d-orbitals
- 7 f-orbitals
can the position of an electron be determined
- no
- no it cannot be mapped exactly
- only the probability of finding an electron in a known region
describe the spins of electrons in an orbital
- two electrons in an orbital that spin in opposite directions
- spin at the same rate
- can only occupy the same orbital if they have opposite spins (paired spins)
what is the shape of the s-orbital
- spherical
what is the shape of the p-orbital
- dumbbell shape
what is the electron configuration of an atom
- the arrangement of electrons in the shells
how are the electrons in shells arranged
- in the lowest energy arrangement possible
- orbitals are filled in order of increasing energy
explain how and why you would write the electron configuration of scandium (Z=21)
- the energy of the 3d subshell lies just above the 4s subshell but just below the 4p subshell
- this means that the 4s orbital is filled before the 3d orbital
- 1s2 2s2 2p6 3s2 3p6 3d1 4s2
how do you know the period of the element according to the electronic configuration
- filling of 2s and 2p corresponds to period 2
- filling of any 3 orbital means period 3 etc.
who proposed the modern periodic table, and describe it
- Dimitri Mendeleev
- 1869
- in his version, the elements were arranged in order of increasing relative atomic mass
- more arranged in order of atomic number
how are the elements arranged in blocks
- group 1-2 S BLOCK
- group 3-0 P BLOCK
- transition metals D BLOCK
- bottom section F BLOCK
what is periodicity
- the occurrence of periodic patterns
what s the reason for the zig zag line in periodic table
- elements to the right of the zig zag line are non metals and do not conduct electricity
- elements to the left of the line are metals and do conduct electricity
what are melting or boiling points
- when elements are melted or boiled the bonds, the intermolecular forces need to be over come
- ## the strength of the IM forces is indicated by the melting or boiling point
describe the trend in melting and boiling points across period 3
- melting and boiling points initially increase up to group 3 because there is an increase in the metallic bonding
- as you move across there is an extra electron added to the delocalised sea of electrons
- it slightly decreases at group 4, bonding changes, but still remands high because it is a giant covalent structure so strong IM forces
- elements from phosphorous onwards are simple structures, only joined by Vander Waals forces so they have very low melting points
- decrease from sulphur to chlorine because the molecule size really decreases
what is covalent bonding
- when non-metallic elements react and share electrons between atoms to form a compound
what forms a double covalent bond
O2, CO2
what forms a triple covalent bond
N2, CO
what is a dative covalent bond
- when a pair of shared electrons in a covalent bond both come from one atom
describe the properties of covalently bonded simple molecules
- covalent intramolecular bonds are strong
- BUT electrostatic forces between molecules are weak
- so small amounts of energy are needed to separate one molecule from another
- so they have low melting and boiling points
- there are no charged particles so they do not conduct electricity
- mostly do not dissolve in water
describe a tetrahedral molecule and give examples
- four groups of electrons around the central atom
- electrons stay repel so they stay as far apart as possible
- bond angle is 109.5
- no lone pairs
-e.g. methane
describe a pyramidal molecule
- has four groups of electrons around the central atom but one of them is a lone pair
- electrons repel to stay as far apart as possible
- lone pairs repel more strongly
- bond angle of 107
- e.g. ammonia
describe a linear molecule
- two groups of electrons around the central atom
- bond angles of 180
- e.g. CO2
describe a trigonal planar molecule
- three groups of electrons around the central atom
- bond angle is 120
- e.g. CH2O, C2H4
describe a bipyramidal molecule
- give groups of electrons around the central atom
- one atom above the central atom, one below, and three evenly distributed around the middle
- bond angles of 90 or 120 depending on where they are in the molecule
- e.g. PCl5
describe an octahedral molecule
- six groups of electrons around the central atom
- one on top of the central atom, one below, and four evenly distributed around the middle
- bond angles of 90
- e.g. SF6
