periodicity Flashcards
alkali metals - mp/bp, density, hardness, conductivity
- 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
alkali metals reactivity
- 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
alkali metals reaction with water
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
metal hydroxide pH
- high pH as it is alkaline
- turns universal indicator blue/purple
halogens - mp/bp, conduction
- mp/bp increase as you descend the group because there are more electrons so the LDFs are stronger
- poor conductors of heat and electricity
halogens reactivity
- 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
noble gases - colour, density, mp/bp
- 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
noble gases reactivity
- 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
general formula for metal reacting with water
- metal + water -> metal hydroxide + hydrogen