Chapter 1.4 Arrangement Of Electrons

Question 1

Why do atoms bond

Answer 1

To gain a stable arrangement of outer shell electrons

Question 2

How many electrons can 
S 
P
D
Hold ?

Answer 2

S 2
P 6
D 10

Question 3

What are the 3 rules of writing electron configuration

Answer 3

1 lowest energy level first
2 electrons with the same spin fill the electron first
3 no single orbital can hold more than 2 electrons

Question 4

Show the rise of energy In subshells

Answer 4

Increase in energy

1s 2s 2p 3s 3p 4s 3D 4p 4s 4d

Question 5

How can you tell if the element is in s p d f block

Answer 5

• Looking at the last sub shell and which letter it ends at,

- identifying which sub shell the outermost electron is in

Question 6

What are the factors that affect ionization energy

Answer 6

Nuclear charge,
The more protons there are in the nucleus the more positively charged the nucleus is and the stronger the attraction for the electron,

Distance from nucleus,
Electron close to the nucleus will be much more strongly attracted than one further away,

Shielding,
As the distance between the outer electrons and the nucleus increases so the outer electrons feel less attraction which lessens the pull of the nucleus by inner shells

Question 7

Describe the trends of ionization energy In a periodic table

Answer 7

Ionization energy decreases down group 2

Ionization energy increases across a period

Question 8

Explain why the first ionisation energy of helium is very large

Answer 8

Electron is not shielded from nucleus

Question 9

Write the equations of first and second ionization energy:

Answer 9

First : x(g) = x^+(g) + e^- ,

Second : x^+(g) = x^+2(g) + e^-

Question 10

Predict and explain the general trend in first ionization energy of period 3

Answer 10

Trend : IE increases across period 3,

Explanation : nuclear charge increases, shielding remains the same

Question 11

Why does magnesium have higher ionization energy than aluminum ? (3)

Step 1 write the electronic configuration,
Mention: which element is bigger (who has more shells), shielding effect and distance from nucleus

Answer 11

• Al outer electron is in 3p orbital, 3p orbital has slightly more energy,
• 3p orbital has additional shielding effect given by 3s,
• Al is a bigger atom and has more energy levels,
• Electrons removed further away from the nucleus

Question 12

Predict and explain the general trend in the IE when going down group 2

Answer 12

Trend : decreases,
Explanation: radius of the atom increases so the distance between the nucleus and outer electrons increase,
There are more filled shells between nucleus and the outer electrons,
These shield the outer electrons from the attraction of the nucleus

Question 13

State and explain the trend in atomic radius of the period 3 elements

Answer 13

Trend : decreases,
Explanation: increasing nuclear charge,
Similar shielding effect

Question 14

State the trend in the first IE in group 2

Answer 14

Trend: decreases
Explanation: shielding increases,
Distance between nucleus and outer electrons increase

Question 15

Give one reason why the 2nd iE of silicon is lower than the 2nd IE of aluminum,

Step 1 write the electronic configuration for both and identify where the last electron is being removed from

Answer 15

• electron removed from 3p orbital for silicon which is further away from the nucleus so less energy required

Question 16

Explain why IE of every element is endothermic

Answer 16

Heat energy is absorbed in order to overcome the attraction between electrons and the nucleus

Question 17

Predict whether an atom of 88Sr will have an atomic radius larger, smaller or the same as 87Rb

Answer 17

Trend : smaller,
Explanation: bigger nuclear charge,
Same shielding

Question 18

Explain why the second IE of element X is greater than the first IE of element X (2)

Step 1 write the equation of IE
Step 2 look at the charges, the charge show how many electrons have been lost

Answer 18

• X+ has more protons than X,
• X+ shows that one electron has been lost which makes it smaller compared to X
• electrons has been removed from positive ions

Question 19

State how Element X deviates from the general trend of first IE across period 3,

Step 1 write the electronic configuration

Answer 19

Trend : lower
Explanation: 2 pair of electrons repel from each other in X orbital,
- spin pair repulsion

Question 20

A general trend exist in the first ionization energy of the period 2 elements, identify one element which deviates from this trend

Answer 20

Boron or oxygen

Question 21

Define ionization energy

Answer 21

the amount of energy required to remove one mole of electrons from one mole of gaseous atoms of an element to form one mole of gaseous ions.

Question 22

Identify the element in period 2 that has the highest first ionization energy and explain why (3)

Answer 22

• neon,
• greatest nuclear charge,
• stable arrangement of outer electrons,
• required very high energy

Question 23

This question is about Period 3 of the Periodic Table. Deduce which of Na+2 and Mg+2 is the smaller ion.
Explain your answer. (2)

Answer 23

Smaller ion: Mg +2

Explanation: Mg+2 has more protons, greater nuclear charge