Topic 8
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Periodic table
An arrangement of elements in periods and groups in order of increasing proton/atomic number
Periodic trends: metallic character
Decreases as you move across period (left to right)
Periodic trends: group number
Corresponds number of outermost electrons + tells us charge -> group 1 elements from 1+ ions and Group 7 elements from 1-
Periodic trends: elements in the same group
Similar chemical properties -> due to having the same number of electrons in their outer shell (chemical peoperties depend on outermost electrons)
Physical properties of alakli metals (group 1)
• Silvery coloured metals • Soft -> easily cut with a knife • Low melting and boiling point • Low densisties
Chemical properties of alkali metals (group 1)
• highly reactive metals • oxidises easily • reactivity increases on descending the group
Observations of reaction with water (group 1 metals) -> lithium
• when cut it reveals a shiny surface • fizzing, floating • when adding universal indicator it turns blue/purple • positive test for hydrogen
Observations of reaction with water (group 1 metals) -> sodium
• floating around surface, fizzing • turns into a perfect sphere as its melting • when adding universal indicator, turns blue/purple • positive test for hydrogen
Observations of reaction with water (group 1 metals) -> potassium
• lilac flame • floating, moving faster • fizzing • forms sphere
Equation of reaction of group 1 metal with water
Metal + water -> metal hydroxide + hydrogen
KEY PROPERTIES metal group 1 -> melting point
• as you go down group 1, the melting point decreases due to weaker forces of attraction (between metal atoms)
KEY PROPERTIES metal group 1 -> denisty
• As you go down group 1, denisty increases
KEY PROPERTIES metal group 1 -> reactivity
As you go down group 1 reactivity increases because: - greater distance between nucleus and outer shell electron - attraction becomes weaker (nuclear attraction) - greater shielding effect - atoms get larger SO: EASIER TO LOSE OUTER SHELL ELECTRON
Halogens (group 7)
• Increasing denisty • non-metals so don’t conduct electricty • exist as diatomic molecules • decreasing reactivity
Physical state of halogens changes as you go down the group -> chlorine
Pale yellow-green gas
Physical state of halogens changes as you go down the group -> flourine
Yellow gas
Physical state of halogens changes as you go down the group -> bromine
Red/brown liquid
Physical state of halogens changes as you go down the group -> iodine
Grey/black solod
Group 7 elements get LESS reactive as you go down the group because?
• larger atoms • weaker attraction between nucleus and outer shell (nuclear attraction) • greater shielding effect • HARDER to gain electron
Properties of transition metals
• high densities -> higher than grouo 1 alkali metals • high melting points -> higher than group 1 alkali metals • stronger than group 1 alkali metals • form coloured compounds • often act as catalysts as elements in compounds • hard, strong and brittle
Noble gasses (group 0 elements)
• unreactive and don’t easily form molecules -> have a full outer shell • stable arrangements of electrons • all of them have 8e- in outer shell, except helium which has 2
Uses of noble gasses
• neon lights • manufactiring of halogen headlights