2.1 Periodicity Flashcards

1
Q

The periodic table is arranged by ____ _____

A

Atomic number

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2
Q

Name the blocks

A
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3
Q

Elements within a period have same number of _____ ___

A

electron shells

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4
Q

Using the periodic table, write the electron configuration for phosphorus

A
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5
Q

Using the periodic table, write the electron configuration for cobalt

A
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6
Q

Atomic Radius _____ across a Period

A

decreases

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7
Q

Why does atomic radius decreases across a period?

A
  • As number of proton increases, positive charge of nucleus increases
  • Increased attraction between nucleus and electrons
  • Similar shielding in each period
    • As electrons added to same outer shell
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8
Q

Why don’t the extra electrons that element gains across period provide extra shielding?

A
  • Extra electrons are added to outer energy level
  • (Shielding is mainly provided by electrons in inner shells)
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9
Q

As you go across period 3, from sodium to magnesium to aluminium, why does melting and boiling points increase?

A
  • ∵ metal-metal bonds get stronger
  • Get stronger ∵ metal ions have increasing positive charge = increasing number of delocalised electrons and decreasing radius
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10
Q

Why does silicon have such a high melting point?

A
  • Silicon is macromolecular (tetrahedral structure) = many strong covalent bonds
  • Lot of energy needed to break these bonds
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11
Q

Why does phosphorus, sulfur and chlorine have low melting points?

A
  • They’re molecular substances so melting points depend upon strength of van der Waals forces between molecules
  • Van der Waals forces are weak and easily overcome
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12
Q

Why does sulfur have a higher melting point than phosphorus or chlorine? (2)

A
  • Sulfur is the biggest molecule (largest Mr)
  • Stronger van der Waals forces between molecules (they’re stronger with larger Mr)
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13
Q

Why does argon have a very low melting point?

A

∵ exists as individual atoms = weak van der Waals forces

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14
Q

Ionisation energy generally ______ across a period

A

increases

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15
Q

Why does ionisation energy generally increases across a period (4)

A
  • As number of proton increases, positive charge of nucleus increases
  • Increased attraction between nucleus and electrons
  • Similar shielding in each period
    • As electrons added to same outer shell
  • More energy needed to remove electron
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16
Q

Predict the element in Period 3 that has the highest second ionisation energy. Give a reason for your answer. (2)

A
  • Sodium / Na
  • Electron (removed) from the 2nd shell / 2p (orbital)
17
Q

Explain why the ionisation energy of every element is endothermic (1)

A

Energy needed to overcome attraction between nucleus and electron