5.3.1 Transition elements (not complete)

What 3-d-block elements form unusual electron configurations?

• Cr

• Cu

What is the electron configuration of Cr?

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5

What is the electron configuration of Cu?

1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10

Why does Cr only have one 4s electron?

it is one away from having a half full 3d subshell so by only having 1 4s electron, it can have a half full 3d subshell so it has overall lower energy

Why does Cu only have one 4s electron?

it is one away from having a full 3d subshell so by only having 1 4s electron, it can have a full 3d subshell so it has overall lower energy

What is the definition of a transition element?

a d-block element that forms an ion with an incomplete d sub-shell

Where do d-block elements lose their electrons from when forming ions?

4s subshell then 3d subshell

Which d-block elements are not transition metals?

• scandium

• zinc

Why isn’t Sc a transition metal?

• it only forms one ion (Sc3+)

• This has an empty 3d subshell and therefore isnt a transition metal

Why isn’t Zn a transition metal?

• it only forms one ion (Zn2+)

• This has an full 3d subshell and therefore isnt a transition metal

What is used to test for transition metals in precipitation tests?

aqueous sodium hydroxide

What is the general positive result for the presence of transition metal ions?

a coloured precipitate forms

What is the general ionic equation for transition metal precipitation reactions?

M n+ + nOH- → M(OH)n (s)

What is the colour of aqueous CU2+ solution?

blue

What is the colour of aqueous Fe2+ solution?

light green

What is the colour of aqueous Fe3+ solution?

yellow

What is the colour of aqueous Mn2+ solution?

pale pink

What is the colour of aqueous Cr3+ solution?

violet

What is the colour of CU2+ precipitate?

blue

What is the colour of Fe2+ precipitate?

green

What is the colour of Fe3+ precipitate?

rusty brown

What is the colour of Mn2+ precipitate?

light brown

What is the colour of Cr3+ precipitate?

grey-green

What is the ionic equation for the CU2+ precipitation reaction?

Cu2+ (aq) + 2 OH- (aq) → Cu(OH)2 (s)

What is the ionic equation for the Fe2+ precipitation reaction?

Fe2+ (aq) + 2 OH- (aq) → Fe(OH)2 (s)

What is the ionic equation for the Fe3+ precipitation reaction?

Fe3+ (aq) + 3 OH- (aq) → Fe(OH)3 (s)

What is the ionic equation for the Mn2+ precipitation reaction?

Mn2+ (aq) + 2 OH- (aq) → Mn(OH)2 (s)

What is the ionic equation for the Cr3+ precipitation reaction?

Cr3+ (aq) + 3 OH- (aq) → Cr(OH)3 (s)

What is the name of the precipitate formed in a copper and sodium hydroxide precipitation reaction?

copper hydroxide

What is the name of the precipitate formed in a iron (II) and sodium hydroxide precipitation reaction?

iron (II) hydroxide

What is the name of the precipitate formed in a iron (III) and sodium hydroxide precipitation reaction?

iron (III) hydroxide

What is the name of the precipitate formed in a manganese and sodium hydroxide precipitation reaction?

manganese (II) hydroxide

What is the name of the precipitate formed in a chromium and sodium hydroxide precipitation reaction?

chromium (III) hydroxide