chemistry f4 bab4

• Scientists' contributions to the development of the periodic table:

  • Antoine Lavoisier: Grouped elements into gas, metal, non-metal, and metal oxide categories
  • Johann W. Dobereiner: Grouped elements into triads and discovered the relationship between relative atomic mass in each triad
  • John Newlands: Arranged elements by increasing nucleon number, known for the law of octaves
  • Lothar Meyer: Calculated atom volume by dividing mass with density
  • Dmitri Mendeleev: Arranged elements by increasing atomic mass
  • Henry G.J. Moseley: Bombarded elements with high-energy electrons, plotted X-ray frequency against proton number
• the elements are arranged in order of increasing proton number
• this order is also related to the electron arrangement of the elements
• the periodic table is a classification of the elements based on their chemical properties
• • There are 18 groups of elements.
  • Group 1: Elements (Li, Na, K, Rb, Cs, Fr) are called alkali metals
  • Group 2: Element known as alkaline earth metal (Be, Mg, Ca, Sr, Ba, Ra)
  • Group 17: Elements (F, Cl, Br, I, At) are known as halogen

   
• • All members of the same group have the same number of valence electrons.
  • The number of the period is indicated by the number of shells filled with electrons.
• Elements in Group 18, also known as inert gases or noble gases, include:

  • Helium (He)
  • Neon (Ne)
  • Argon (Ar)
  • Krypton (Kr)
  • Xenon (Xe)
  • Radon (Rn)
• Physical properties of Group 18 elements:

  • Insoluble in water
  • Do not conduct electricity
  • Do not conduct heat
  • Boiling and melting points increase down the group
  • Van der Waals forces increase as the size of the atoms increases
• Chemical properties of Group 18 elements:

  • Do not react with other elements
  • Exist as monatomic (single atom)
  • Inert gases are non-reactive because the valence shell is full
  • Helium has a stable duplet electron arrangement with two valence electrons
  • Other Group 18 elements have a stable octet electron arrangement with eight valence electrons
  • Noble gases do not accept or donate electrons as they are already stable
• Element As going down the groupLi

  • The atomic radius increases.  
  • Density increases.
  • The melting point decreases.
  • Electeopositivity also increase
  • The attractive force between the nucleus and the single electron decreases as the radius increases.

   
• physical properties of group 1: soft metal and good conductors of heat and electricity
• Elements in Group 1, also known as alkali metals, include: Hydrogen, Lithium, Sodium, Potassium, Rubidium, Caesium, and Francium
• Physical properties of Group 1 elements:

  • Soft metals
  • Good conductors of heat and electricity
• Chemical properties of Group 1 elements:

  • React with water to produce hydrogen gas and alkaline solution
  • React with oxygen to produce metal oxide
  • React with halogens to produce metal halides
• Reactivity of Group 1 elements:

  • Very reactive as going down the group
  • Tend to donate an electron and become positive ions
  • The donation of an electron aims to attain a stable duplet or octet electron arrangement
  • The atomic radius increases down the group, weakening the force between the nucleus and the electron, making it easier to be donated or released
• elements in group 17- also known as halogen, very reactive elements
• • The elements in this group are; 
  • Fluorine, F
  • Chlorine, Cl
  • Bromine, Br
  • Iodine, I
  • Astatine, At
  • Tennessine, Ts
• the physical properties of G17 is non-metal and does not conduct heat and electricity
• As going down the group

  • The atomic radius increases.  
  • Reactivity decreases.
  • Boiling and melting point increases.
  • The van der Waals force increases as the size of the atom increases.
  • The electronegativity decreases because the radius increases and the force between the valence electron and nucleus decreases.

   
• • Group 17 is very reactive, but the reactivity decreases down the group.
  • The elements will accept an electron to achieve a stable octet electron arrangement.
  • The forces between the nucleus and the valence electron become weaker as going down the group.
• • The elements in Period 3 will show a gradual change in physical and chemical properties, as going across the period. 
• • The elements in Period 3 are; 
  • Sodium, Na
  • Magnesium, Mg
  • Aluminium, Al
  • Silicon, Si
  • Phosphorus, P
  • Sulphur, S
  • Chlorine, Cl
  • Argon, Ar
• • Atomic radius decreases:
  • There are only three shells, but the number of electron increases.
  • The increase in the number of electrons means there is an increase in the number of protons, which result in the higher electrostatic force.
  • The increase of electrostatic force pulls the valence electron closer to the nucleus.
• • The number of valence electrons increases:
  • The number of electrons of the element increases.  
• • The electronegativity increases:
  • The atomic radius decreases as the number of protons increases.
  • As the number of protons increases, the electrostatic force also increases and creates a tendency to attract electrons.
  • The left side of the period is less electronegative than the right side of the period.
• • The melting point and boiling point:
  • Increases from the left to the middle of the period, and then decrease again.
• • Nature of metals:
  • The elements change from metal to metalloid, and then non-metal as the electronegativity increases.
• • Nature of oxides:
  • The oxides of the elements change from basic to amphoteric and then to acidic across the period.
• Position of transition elements in the Periodic Table from Group 2 until Group 12.
• • The transition metal is metal that has some characteristics:
  • High density
  • High hardness
  • Silvery surface
  • High tensile strength
  • High conductivity
  • Ductile and malleable
  • High melting point
  • High boiling point
• Special properties of transition elements- have more than one oxidation number, can form coloured compounds, can function as a catalyst to increase the rate of reaction
• Iron (Fe):

  • Used as a catalyst in the Haber Process to produce ammonia (3NH3​)
  • Used to build bridges
• Platinum (Pt):

  • Used as a catalyst in the Ostwald Process to produce nitric acid (HNO3​)
• Vanadium(V) oxide (V2​O5):

  • Used as a catalyst in the Contact Process to produce sulphuric acid (H2​SO4)
• Nickel (Ni) or Platinum (Pt):

  • Used as a catalyst in the hydrogenation process on vegetable oils to produce margarine
• Manganese (Mn):

  • Used to make stained glass windows
• Titanium (Ti):

  • Used to make paints