periodicity Flashcards

1
Q

alkali metals - mp/bp, density, hardness, conductivity

A
  • mp/bp: decrease as you descend the group because the distance of the delocalised electrons to the nucleus increases, so metallic bond strength decreases
  • density: generally increases as you descend the group due to the increasing masses of the nuclei
  • hardness: become softer as you descend the group due to the decreasing strength of metallic bonding
  • conductivity: good conductors of heat and electricity due to the presence of delocalised electrons
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2
Q

alkali metals reactivity

A
  • very reactive as they only have to lose one electron to become stable
  • the elements have to be stored in oil to prevent them from reacting with oxygen and water in the air
  • when exposed to the air, the shiny metals will quickly react with oxygen and tarnish, forming metal oxide
  • descending group 1, the elements become more reactive because less energy is required to remove the electron
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3
Q

alkali metals reaction with water

A

lithium: reacts slowly, floats, gradually dissolves, lithium hydroxide formed, H2 given off which burns with a red flame when ignited
sodium: reacts more quickly, quickly dissolves, sodium hydroxide formed, H2 given off which burns with a yellow-orange flame when ignited
potassium: reacts vigorously, very quickly dissolves, potassium hydroxide formed, H2 given off which burns with a lilac flame when ignited

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4
Q

metal hydroxide pH

A
  • high pH as it is alkaline

- turns universal indicator blue/purple

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5
Q

halogens - mp/bp, conduction

A
  • mp/bp increase as you descend the group because there are more electrons so the LDFs are stronger
  • poor conductors of heat and electricity
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6
Q

halogens reactivity

A
  • highly reactive as they only need 1 more electron
  • reactivity decreases as you descend the group because the atoms get larger, so the incoming electron joins a shell that is further from the nucleus -> has a weaker force of attraction to the nucleus
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7
Q

noble gases - colour, density, mp/bp

A
  • all colourless at room temp and pressure
  • very low mp/bp which increase as you descend the group due to more electrons -> stronger LDFs
  • density increases as you descend the group due to increasing mass of atoms
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8
Q

noble gases reactivity

A
  • very un-reactive because they have a full outer electron shell
  • therefore, they exist as single atoms (monatomic)
  • described as being inert (chemically inactive)
  • some compounds of noble gases at the bottom of the group have been made, e.g. XeF4, KrF2 but only with the most reactive of the non-metal elements
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9
Q

general formula for metal reacting with water

A
  1. metal + water -> metal hydroxide + hydrogen
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