Atoms and electrons

Question 1

What is meant by principal quantum number?

Answer 1

The number of each main energy level: n

Question 2

How do we work out the maximum number of electrons that each energy level can hold?

Answer 2

2n2

Question 3

Define atomic orbital

Answer 3

A region around the nucleus that can hold up to two electrons with opposite spins, a down or an up spin.

Question 4

What are electrons considered to be as?

Answer 4

A cloud of negative charge

Question 5

Give the several different types of atomic orbitals

Answer 5

S,P,D,F

Question 6

Give the characteristics of each shape of atomic orbital

Answer 6

S orbitals are shaped spherically whereas P orbitals are shaped like dumbbells

Question 7

How many S orbitals are there in each energy level?

Answer 7

There are 1 in each energy level

Question 8

How many P orbitals are there in each energy level?

Answer 8

Each electron shell apart from the first one has 3 P orbitals

Question 9

How many D orbitals are there in each energy level?

Answer 9

Every shell apart from shells 1 and 2 have 5 D orbitals

Question 10

How many F orbitals are there in each energy level?

Answer 10

Seven different F orbitals in shells 4 and above

Question 11

What is the max number of electrons in each energy level of a shell?

Answer 11

1=2 , 2=8 ,3=18 , 4= 32

Question 12

What is an atomic sub-level?

Answer 12

All the orbitals of the same type in the same shell

Question 13

Describe the rules for filling atomic orbitals

Answer 13

-Orbitals with the lowest energy are filled first
-We can have two electrons in the same orbital but they must have opposite spins
-If we have orbitals with the same energy then we put electrons in individual orbits before we pair them, this is because electrons in the same orbital repel

Question 14

What order is electron configuration written in?

Answer 14

Order of electron shells not the order of the filling.

Question 15

Why are chromium and copper both exceptions for the electron configuration rules?

Answer 15

The 3D sub- level is most stable when it is either half full or completely full, and because chromium has 1 electron in the 4s sub-level this means it can have a half full 3d sub-level. For copper, by only having one electron in its 4s sub-level, it can have a completely full 3d sub-level.

Question 16

Define first ionisation energy

Answer 16

The energy needed to remove one mole of electrons from one mole of atoms in their gaseous state to form one mole of 1+ ions.( also in their gaseous state)

Question 17

Define second ionisation energy

Answer 17

Energy needed to remove one mole of electrons from one mole of 1+ ions in their gaseous state to form one mole of 2+ ions also in their gaseous state

Question 18

Describe the factors affecting ionisation energy

Answer 18

-The distance between nucleus and outermost electrons ( atomic radius)
-The number of protons in the nucleus, greater number of protons means there is a greater electrostatic force between electrons and the nucleus
-Shielding, the more shielding there is the more reduced the attraction is between the electrons and the nucleus

Question 19

How does first ionisation energy change as you go down a group?

Answer 19

It decreases because the atomic radius increases meaning outer electron shell is further away from the nucleus meaning the electrostatic attraction is decreased, and the number of internal energy levels also increases meaning there is more shielding between nucleus and outer electron shell

Question 20

How does first ionisation energy change as you go across a period?

Answer 20

Increases, because atomic radius decreases across a period which means that outer electrons are more electroststically attracted to the nucleus and the number of protons also increases so attraction is stronger between nucleus and electrons

Question 21

Why might elements not fit in the trend of first ionisation energy along a period and why?

Answer 21

For example, an element may have a pair of electrons in one of their orbitals whereas the element that is expected to have a lower first ionisation energy has their electrons in individual orbitals in a subshell, meaning that when they are paired the electrons repel eachother meaning it takes less energy to remove one of these electrons compared with if they were in individual orbitals
A second example may be because a subshell of an element further along a period may have their electrons in a p or a orbital which may mean theres a lower first ionisation energy

Question 22

What is the key feature of elements electron configuration in block d?

Answer 22

4s subshell fills before 3d subshell however when the 4s subshell contains electrons it has a higher energy than the 3d subshell

Question 23

What are successive ionisation energies?

Answer 23

We can continue to remove electrons and measure the ionisation energies, for example the first electron would need the least amount of energy as it is being removed from a nueral atom, then the second would need more as it is being removed from a 1+ ion and so on.

Question 24

How are electrons arranged in the subshells and main energy levels?

Answer 24

Energy level 1- 1 subshell (1s) holding 2 e
Energy level 2- 2 subshells ( 2s,2p) S holds 2 p holds 6
Energy level 3- 3 subshells ( 3s, 3p,3d) S holds 2 p holds 6 d holds 10
Energy level 4- 4 subshells ( 4s,4p, 4d,4f) S holds 2 P holds 6 D holds 10 f holds 14

Question 25

How does an atom fill up each subshell?

Answer 25

In order of increasing energy ( 3d subshell has a higher energy than 4s so 4s gets filled first 1s-2s-2p-3s-3p-4s-3d-4p-5s-4d-5p

Question 26

What area of the periodic table is S block and what do these elements have in common?

Answer 26

Group 1 and 2, have their outer electrons in an s subshell

Question 27

What area of the periodic table is P block and what do these have in common?

Answer 27

Groups 3 4 5 6 7 and 8 which all have their outer electrons in a p subshell

Question 28

What area of the periodic table is D block and what do these all have in common

Answer 28

Transition metals, have their outer electrons in d subshell

Question 29

Why are sucessive ionisation energies higher?

Answer 29

As when the first electron is removed a positive ion is formed This ion will then increase attraction onto remaining electrons due to a stronger positive charge in the nucleus This means more energy is needed to remove the next electron

Question 30

Give an example of an equation used to represent first ionisation energy

Answer 30

H(g)= H+(g) + e-

Question 31

Give an example of an equation used to represent second ionisation energy

Answer 31

T+ (g) = T2+(g) + e-

Question 32

Explain different ionisation energies needed for electrons in different groups

Answer 32

-An electron in an energy level closer to the nucleus needs a higher ionisation energy to remove this electron as there is a higher electrostatic attraction - Also less electron shielding, stronger attraction to nucleus

Question 33

Why does helium have the largest first ionisation energy?

Answer 33

- Its first electron is in a shell closest to the nucleus and has no shielding effects from closer electrons - Higher ionisation energy than H as it has one more proton

Question 34

Why do first ionisation energies decrease down a group

Answer 34

- As atoms get larger down the group, outer electrons are found in energy levels further from the nucleus, distance is larger - This means attraction to the nucleus is weaker, less energy needed to remove outer electrons

Question 35

Why do first ionisation energies increase across a period

Answer 35

- Number of protons in nucleus increases - Stronger positive charge on nucleus -More attracted to outer electron levels

Question 36

Why does Na(11) have a much lower first ionisation energy than Ne (10)

Answer 36

Na has its outer electron in a 3s subshell further from the nucleus with more shielding, weaker attraction to the nucleus Outer electrons are easier to remove

Question 37

Why is there a small drop in first ionisation energy from Mg(12) to Al (13)

Answer 37

Al is starting to fill a 3p subshell which is further away from the nucleus and has more electron sheilding from the 3s subshell Mg only has electrons in 3s subshell

Question 38

Why is there a small drop in first ionisation energy from from P(15) to S (16)

Answer 38

S has 4 electrons in the 3p subshell and the 4th is filling the first orbital next to another electron This causes electron repulsion,making it easier to remove the first electron from S P has just one electron in each 3p orbital, no repulsion