electrons and ionisation energies

Question 1

define orbital

Answer 1

a region around the nucleus that can hold up to two electrons with opposite spins

Question 2

describe the structure of electrons

Answer 2

-arranged in shells, which are regarded as energy levels.
-orbitals (s, p, d and f)
-sub shells (groups of orbitals of the same type)

Question 3

why does 4s fill up before 3d?

Answer 3

the 3d sub shell is at a higher energy level than the 4s sub shell, so the 4s sub shell fills first (as orbitals fill in order of increasing energy)

Question 4

full electronic configurations

Answer 4

-shows how sub shells are occupied by electrons
full electronic configuration of Lithium (3 electrons):
1s^2 2s^1

Question 5

noble gas electronic configurations

Answer 5

-shorthand electronic configuration
-expressed in terms of the previous noble gas in the periodic table + outer electron sub-shells.
noble gas electronic configuration of Lithium (3 electrons):
[He]2s^1

Question 6

how do you tell the final electron from the periodic table?

Answer 6

-the period number determines the final shell
-the block that the element is in determines the orbital that the electron is in (s, p, d, f)
-the element’s position in the block tells us how many electrons are in the orbital (e.g. calcium is 2nd along in the s block)
e.g. calcium: period 4, s block, 2nd along in s block -> 4s^2 final electron

Question 7

define first ionisation energy

Answer 7

the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

Question 8

what are the trends in ionisation energy across a period?

Answer 8

nuclear charge increases and atomic radius decreases (electron shielding stays constant), so nuclear attraction increases, increasing the first ionisation energy

Question 9

what are the trends in ionisation energy down a group?

Answer 9

atomic radius and electron shielding increases, so nuclear attraction decreases, decreasing the first ionisation energy

Question 10

how do you find the identity of an element from successive ionisation energies?

Answer 10

by studying the jump between successive ionisation energies, the number of electrons in the outer shell can be determined. if there is a significantly larger increase between the third and fourth ionisation energies then this shows that the fourth electron is being removed from an inner shell, so there are three electrons in the outer shell.

Question 11

how many electrons can fill the first four shells?

Answer 11

32

Question 12

describe the shape of a p orbital

Answer 12

a dumbell

Question 13

describe the shape of an s orbital

Answer 13

a sphere

Question 14

how many s orbitals are in an s sub shell, and how many electrons?

Answer 14

one s orbital, 2 electrons

Question 15

how many orbitals are in a p sub shell, and how many electrons?

Answer 15

three p orbitals, 6 electrons (2 x 3)

Question 16

how many orbitals are in a d sub shell, and how many electrons?

Answer 16

five d orbitals, 10 electrons (2 x 5)

Question 17

how many orbitals are in an f sub shell, and how many electrons?

Answer 17

seven f orbitals, 14 electrons (2 x 7)

Question 18

define successive ionisation energy

Answer 18

an atom has as many ionisation energies as there are electrons. each successive ionisation energy will be greater than the first as after one electron is lost, the protons in the nucleus will pull the remaining ones closer, increasing the nuclear attraction between them.

Question 19

describe the trend in first ionisation energy across period 2 and 3

Answer 19

general increase, with 2 decreases between beryllium and boron and nitrogen and oxygen

Question 20

explain the decrease in first ionisation energy between beryllium and boron

Answer 20

the fall in IE marks the start of filling the 2p sub shell. the 2p sub shell in boron has a higher energy than the 2s sub shell in beryllium, so it will be less attracted to the nucleus. therefore, the first ionisation energy of boron will be less than that of beryllium

Question 21

explain the decrease in first ionisation energy between nitrogen and oxygen

Answer 21

the fall in IE marks the start of electron pairing in the p orbitals of the 2p sub shell. in both nitrogen and oxygen, the highest energy electrons are in a 2p sub shell. in oxygen, the paired electrons in the 2p sub shell repel one another, making it easier to remove that electron. therefore, the first ionisation energy of oxygen is lower than that of nitrogen.

Question 22

why are electrons paired in opposite spins?

Answer 22

the opposite spins counteract the repulsion between them

Question 23

how do orbitals with the same energy fill?

Answer 23

they fill singly first, to avoid unnecessary repulsion between paired electrons until there is no further orbital available in the same energy level

Question 24

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