OCR A Chemistry – 'Electron Structure' 2.2.1

How many electrons can fill the first FOUR shells of an atom?

1st Shell = ​ (a)  

2nd Shell = ​ (b)  

3rd Shell =​ (c)  

4th Shell = ​ (d)  

• 2
• 8
• 18
• 3
• 4
• 5
• 6
• 7
• 9
• 32

Answer explanation

2.2.1(a)

REMEMBER that "each new shell includes a new sub-shell"

name the subshells in order that they are filled

1st to be filled =​ (a)  

2nd to be filled =​ (b)  

3rd to be filled =​ (c)  

4th to be filled =​ (d)   ​

• s
• p
• d
• f
• g
• a
• b
• x
• y
• z

How many electrons does each sub-shell hold?

s = ​ (a)  

p = ​ (b)  

d = ​ (c)  

f = ​ (d)  

• 2
• 6
• 10
• 14
• 4
• 1
• 8
• 18
• 12
• 16

Answer explanation

2.2.1(a) "the number of electrons that can fill the first four shells"

Elements are arranged into "blocks" on the periodic table.

Which block is two groups wide?

Elements are arranged into "blocks" on the periodic table.

Which block is 4 periods high?

How many orbitals does each hold

s =​ (a)  

p =​ (b)  

d =​ (c)  

f = ​ (d)  

• 1
• 3
• 5
• 7
• 2
• 6
• 10
• 14
• 4
• 8

Answer explanation

2.2.1(a) "the number of electrons that can fll the frst four shells"

Which is the best definition of an ATOMIC ORBITAL

• a region around the nucleus that can hold two electrons, with opposite spins

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

• an energy level in an atom that can hold up to two electrons, with opposite spins

• a nuclear region that can hold up to two electrons, with opposite spins

Answer explanation

2.2.1(b)

Always learn definitions/explanations in the spec... word-for-word!

TICK ALL ACCEPTABLE drawings of a p-orbital

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• 
• 
• 
• 

Answer explanation

2.2.1 (b) (i)

"the shapes of s- and p-orbitals"

Write the symbol for the sub-shell that is filled next:

1s,2s,2p,3s,3p,4s,3d,...

Write the symbol for the sub-shell that is filled next:

1s,2s,2p,3s,3p,...