Electrons

Question 1

how can electrons be presented

Answer 1

electrons in different shells have different amounts of energy

they can therefore be represented on an energy level diagram

Question 2

define electron shells

how do we find out how many electrons are in each shell

Answer 2

the shells are called main energy levels and they are labelled 1, 2, 3, and so on

each main energy level can hold up to a maximum number of electrons given by the formula 2n^2

Question 3

what are the main energy levels divided into

Answer 3

the main energy levels are divided into sublevels S, P, D and F which have slightly different energies

Question 4

what sub levels does level 2 have

Answer 4

s-sub levels
P-sub levels

Question 5

what sub levels does level 3 have

Answer 5

s-sub levels, a p-sub-level and a d-sub-level

Question 6

what is quantumn mechanics used for

Answer 6

for a more complete description of the electrons in atoms quantum mechanics is used

this was developed in the 1920s

Question 7

what does quantum mechaniques do

Answer 7

describes the atom mathematically with an equation ( the Schrodinger equation).

Question 8

describe the solutions to the Schrodinger equation

Answer 8

the solutions to this equation give the probability of finding an electron in a given volume of space called an atomic orbital

Question 9

define an electron

explain what it does

Answer 9

a cloud of negative charge

an electron fills a volume in space called its atomic orbital

Question 10

describe atomic orbitals

Answer 10

different atomic orbitals have different energies. each orbital has a number that tells us the main energy level that it corresponds to

the atomic orbitals of each main level have different shapes, which in turn have slightly different energy.

these are the sublevels described by the letters S, P, D, AND F

Question 11

What does the shape of the orbital represent

Answer 11

a volume of space in which there is a 95% probability of finding an electron and they influence the shapes of molecules

Question 12

describe the sub-levels in each of the first main energy levels

Answer 12

the first main energy level consists of a single s-orbital.

the second main level has a single s-orbital and three p-orbitals of slightly higher energy, t

The third main level has a single s-orbital, three p-orbitals of slightly higher energy, and five d-orbitals of slightly higher energy still

Question 13

how many electrons can any single atomic orbital hold

Answer 13

any single atomic orbital can hold a maximum of 2 electron

Question 14

how many electrons does an s-orbital hold

Answer 14

up to two electrons

Question 15

how many electrons can p orbitals hold

Answer 15

p-orbitals can hold up to 2 electrons each, but always come in groups of three of the same energy, to give a total of up to six electrons in the P-sublevel

Question 16

how many electrons can d orbitals hold

Answer 16

d-orbitals can hold 2 electrons each, but come in groups of three of the same energy, to give a total of up to 10 electrons in the d-sub level

Question 17

how many electrons are in the 1st energy level

Answer 17

the first main energy level has an s-sub-level with 1 orbital in it. therefore the total number of electrons is 2

Question 18

how many electrons are in the second energy level

Answer 18

sub-levels in the second energy level are s and p

number of orbitals in s is 1 (2e-)

number of orbitals in p is 3 (6e-)

therefore the total number of electrons in the main energy level is 8

Question 19

how many electrons are in the 3rd energy level

Answer 19

sub levels in the 3rd energy level are S, P, and D
number of orbitals in S is 1 (2e-)

number of orbitals in P is 3 (6e-)

number of orbitals in D is 5 (10e-)

therefore the total number of electrons in main energy level is 18

Question 20

how many electrons are in the 4th energy level

Answer 20

sub levels are s p d and f

number of orbitals in s is 1 (2e-)

number of orbitals in p is 3 (6e-)

number of orbitals in d is 5 (10e-)

number of orbitals in f is 7 (14e-)

therefore the total number of electrons in main energy level is 32

Question 21

explain the spin property in electrons

Answer 21

two electrons in the same orbital must have opposite spins

the electrons are usually represented by arrows pointing up or down to show the different directions of spins

Question 22

what are the three rules for allocating electrons to atomic orbitals

Answer 22

atomic orbitals of lower energy are filled first so the lower main energy level is filled first and , within this level, sub-levels of lower energy are filled first

atomic orbitals of the same energy sill single before pairing starts. this is because electrons repel each other

no atomic orbitals can hold more than two electrons