perodic table.pdf#page=1&rect=15,75,758,487

info from table

• Group
  • A group is a vertical column of elements with similar chemical properties
  • Elements in the same group have the same number of valence electrons
    • This number is the number of the last digit of the group
  • Elements in the same group have similar chemical properties due to their similar valence shell electronic configuration
  • Elements in the same group generally form ions of the same charge and form compounds with similar formulae
• Period
  • A group is a horizontal row of elements
  • Elements in the same period have the same number of principal quantum shells
  • There is a periodic change in their chemical properties across the period

Periodic trends

Metallic and non-metallic character across a period

• Elements on the left of the periodic table are metals, while those on the right are non-metals
• From left to right across a period, there is a decrease in metallic properties and an increase in non-metallic properties
• A metalloid is an element with properties that are at the dividing line between those of metals and non-metals

Nature of oxides

• In general
  • Metals form basic oxides
  • Non-metals for acidic oxides
  • Metalloids form amphoteric oxides
• However, there are exceptions. Some metals such as aluminium form an amphoteric oxide, $\ce{Al2O3}$, and the metalloid, silicon, form an acidic oxide, $\ce{SiO2}$

Ionic charge

• The elements in Group 1, 2 and 13 are metals and they form cations (positively charged ions)
• The metals lose their valence electrons to form positive ions
• The elements in Group 15, 16, and 17 are non-metals and tend to form covalent compounds when they combine with non-metals
  • However, when they combine with Group 1 and 2 metals, they form ionic compounds
  • To form an ionic compound, the non-metals form anions (negatively charged ions)
    • The charge on the anion corresponds to the group number minus eighteen

Groups

Group 1

Alkali Metals

• physical properties
  • They are silver and shiny but are grey when exposed to air
  • Atomic radii increase down the group
  • Density increases down the group
    • $\ce{Li}$, $\ce{Na}$, $\ce{K}$ are less dense than water, $\ce{Rb}$, $\ce{Cs}$ are denser than water
      • however $\ce{K}$ is less dense than $\ce{Na}$
    • As atomic radii increases faster than atomic volume
  • Are relatively soft and can be cut easily with a knife
  • Have low melting and boiling points compared to other metals
    • Melting and boiling points decrease down the group
      • As larger atomic radius decreases EFOA between sea of delocalised electrons and metal cations
  • Good conductors of heat and electricity in solid and molten states

• Chemical properties
  • Are very reactive and react rapidly with air and vigorously with water
    • are kept under (paraffin) oil to prevent contact with water and air
  • Are called alkali metals as they react readily with water to form alkalis
  • Reactivity increases down the group
    • Down a group
      • Atomic radii increases due to more occupied electron shells
      • Metal atoms lose valence electron more readily ( $1^{\text{st}}$ ionisation energy decreases ) as valence electron is further away from the nucleus and less strongly attracted
      • Therefore EFOA between nucleus and valence electron becomes weaker, less energy is required to remove the valence electron, and $\ce{M+}$ cations form more easily

Reactions with water

• All group 1 metals react with cold water to form alkalis (soluble metal hydroxides) $\ce{2M(s) + 2H2O(l) -> 2MOH(aq) + H2(g)}$

Reactions with oxygen

• All group 1 metals react when ignited in air
• Group 1 oxides are solids at room temperature $\ce{4M(s) + O2(g) -> 2M2O(s)}$

Group 17

• Halogens
  • Halogens are non-metals and exist as diatomic covalent molecules
  • Their ions are known as halide ions
  • Physical properties
    • Have low melting and boiling points
    • Coloured and non-conductors of electricity
    • Down the group, colour intensity increases, melting and boiling points increase, and volatility decreases
      • will test colour during exam, espacially aq with displacement reaction
        • Table below is for halogen, halide solutions are all colourless
      • Halogens have simple molecular structure
      • down a group, electron cloud size increases
  • Chemical Properties
    • Reactivity decreases down the group
      • Halogens form ions by gaining one electron
      • Atomic radii increases as number of occupied principal quantum shells increases
      • Increased atomic radii decreases EFOA between nucleus and valence electrons
      • Halogens gain electrons less readily
    • are powerful oxidising agents because they gain electrons readily to form halide ions
      • Oxidising power decreases down a group

Reactions

• Halogens react vigorously with metals to form metal halides, which are ionic compounds; e.g. $\ce{2Fe(s) + 3Cl2(g) -> 2FeCl3(s)}$
• They also react with non-metals to form covalent compounds; e.g. $\ce{H2(g) + Cl2(g) -> 2HCl(g)}$
• Displacement reaction
  • A more reactive halogen displaces a less reactive halogen from its halide solution
    • Reaction is exothermic
    • Usually only consider $\ce{I2}$, $\ce{Br2}$, $\ce{Cl2}$ as $\ce{F2}$ is too violently reactive and $\ce{At2}$ is rare and radioactive
    • When describing colour, state the colour change from the halide solution (reactants) to the halogen solution (products)

Example

Halogen	$\ce{KCl(aq)}$	$\ce{KBr(aq)}$	$\ce{KI(aq)}$
$\ce{Cl2(aq)}$	–	Orange solution formed from a colourless solution. $\ce{Cl2(aq) + 2Br^-(aq) -> 2Cl^-(aq) + Br2(aq)}$	Brown solution formed from a colourless solution. $\ce{Cl2(aq) + 2I^-(aq) -> 2Cl^-(aq) + I2(aq)}$
$\ce{Br2(aq)}$	No reaction	–	Brown solution formed from a colourless solution. $\ce{Br2(aq) + 2I^-(aq) -> 2Br^-(aq) + I2(aq)}$
$\ce{I2(aq)}$	No reaction	No reaction	–

Uses

• Fluorine
  • Added to tap water and toothpaste to kill bacteria and prevent tooth decay
• Chlorine
  • Added to swimming pool and tap water to kill microorganisms and bacteria
  • Chloride salt in food replaces those lost in sweat and urine, with two-thirds of the anions in human blood being chloride ions
  • Used as a bleaching agent and in the preparation of drugs and insecticides
• Iodine
  • Needed in small amounts as a food supplement as deficiency can cause goitre
  • Present naturally in seafood

Group 18

• noble gases or inert gases
  • are odourless, colourless at room temperature and pressure
  • Have low melting and boiling points
    • increases down a group due to increased atomic radii and stronger dispersion forces
  • have low densities
    • Density increases down the group
      • Atomic mass increases faster than atomic volume
  • Have stable electronic configuration as their outermost electron (valence) shell is full
    • $\ce{He}$ has a duplet electronic configuration
    • Other noble gases have a octet electronic configuration
    • They are inert (chemically unreactive)

Uses

• Helium
  • Used to fill airships and weather balloons (replacing hydrogen)
  • A mixture of helium (80%) and oxygen (20%) is used in diver's oxygen tanks (replacing nitrogen, which dissolves in blood causing decompression sickness called 'the bends')
  • Liquid helium is used to cool metals into superconductors
• Neon
  • Used in advertising lights and television tubes
• Argon
  • Used to fill light bulbs
  • Used as a carrier gas in gas-liquid chromatography
• Xenon
  • Used for making electron tubes and stroboscopic lamps
  • Used in bubble chambers in atomic energy reactors
• Radon
  • Used in the treatment of cancer
• Krypton
  • Used in lasers to repair the retina of the eye
  • Used to fill photographic flash lamps

Transition metals

• A transition element is a d-block element whose atom has an incomplete d-subshell, or which can give rise to cations with an incomplete d-subshell
  • Therefore $\ce{Zn}$ is excluded from the class of transition metals
  • $\ce{Sc^3+}$ and $\ce{Zn^2+}$ are excluded as their compounds solutions are colourless
    • cos of lack of electrons in d-orbital in $\ce{d -> d}$ transition
• Physical properties

• Chemical properties