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    Periodic Table of Elements Chapter

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    Reo Rando
    The elements in group 1 are known as alkali metals. They are soft, with low melting and boiling temperatures. They have low densities - Li, Na and K are less dense than water. They show relatively weak metallic bonding as only one electron is available from each atom. The fall in Melting and Boiling Points reflects the fall in the strength of the metallic bond.

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    Periodic Table of Elements Chapter

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    Reo Rando
    211 views10 pages
    The elements in group 1 are known as alkali metals. They are soft, with low melting and boiling temperatures. They have low densities - Li, Na and K are less dense than water. They show relatively weak metallic bonding as only one electron is available from each atom. The fall in Melting and Boiling Points reflects the fall in the strength of the metallic bond.

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    The elements in group 1 are known as alkali metals. They are soft, with low melting and boiling temperatures. They have low densities - Li, Na and K are less dense than water. They show relatively weak metallic bonding as only one electron is available from each atom. The fall in Melting and Boiling Points reflects the fall in the strength of the metallic bond.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    211 views10 pages

    Periodic Table of Elements Chapter

    Uploaded by

    Reo Rando
    The elements in group 1 are known as alkali metals. They are soft, with low melting and boiling temperatures. They have low densities - Li, Na and K are less dense than water. They show relatively weak metallic bonding as only one electron is available from each atom. The fall in Melting and Boiling Points reflects the fall in the strength of the metallic bond.

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    Download as pptx, pdf, or txt
    of 10

    PERIODIC TABLE OF ELEMENTS

    CHAPTER 4
    CHEMISTRY
    PERIODIC TABLE OF ELEMENTS
    (C)- GROUP 1 ELEMENTS

    CHAPTER-4
    © GROUP 1 ELEMENTS
    GROUP 1-ELEMENTS
    The elements in Group 1 are known as alkali metals..
    These elements include;
    ELEMENTS SYMBOLS Relative atomic mass

    LITHIUM Li 7

    SODIUM Na 23

    POTASSIUM K 39

    RUBIDIUM Rb 85.5

    CAESIUM Cs 133

    FRANCIUM Fr 223
    The physical properties of group 1
    elements
    The alkali metals differ from other metals in several ways. They are soft, with low
    melting and boiling temperatures. They have low densities - Li, Na and K are less dense
    than water. They have low standard enthalpies of melting and vaporization. They show
    relatively weak metallic bonding as only one electron is available from each atom.
    Alkali metals colour flames. When the element is placed in a flame the heat provides
    sufficient energy to promote the outermost electron to a higher energy level. On
    returning to ground level, energy is emitted and this energy has a wavelength in the
    visible region:

    Li red Na yellow K lilac Rb red Cs blue

    The ionic radii of the alkali metals are all much smaller than the corresponding ionic radii.
    This is because the atom contains one electron in an s level relatively far from the
    nucleus in a new quantum shell, and when it is removed to form the ion the remaining
    electrons are in levels closer to the nucleus. In addition, the increased effective nuclear
    charge attracts the electrons towards the nucleus and decreases the size of the ion.
    Trends in Melting and Boiling Points

    You will see that both the melting points and boiling points fall as you go down the
    Group.
    Explaining the trends in melting and boiling points
    When you melt any of these metals, the metallic bond is weakened enough for the
    atoms to move around, and is then broken completely when you boil the metal.
    The fall in melting and boiling points reflects the fall in the strength of the metallic
    bond.
    The atoms in a metal are held together by the attraction of the nuclei to the delocalised
    electrons. As the atoms get bigger, the nuclei get further away from these delocalised
    electrons, and so the attractions fall. That means that the atoms are more easily pulled
    apart to make a liquid and finally a gas.
    In the same way that we have already discussed, each of these atoms has a net pull
    from the nuclei of 1+. The increased charge on the nucleus as you go down the Group is
    offset by additional levels of screening electrons. All that matters is the distance
    between the nucleus and the bonding electrons.
    CHEMICAL PROPERTIES OF GROUP
    1 ELEMENTS
    Lithium,sodium and potassium have similar chemical properties but differ in reativity.

    Alkali metals react vigorously with water to produce alkaline metal hydroxide solutions
    and hydrogen gas,H2.for example;
    2Li(s)+2H2O(I) 2LiOH(aq)+H2(g)
    The reactions between alkali metals and oxygen gas,O2
    Alkali metals burn in oxygen gas,O2 rapidly to produce white solid metal oxides.for
    example;
    4Li(S)+O2(g) 2Li2O(s)
    The alkali metals burn more vigorously from lithium to potassium.the solid metal oxides
    formed can dissolve in water to form alkaline metal hydroxide solutions.
    Li2O(s)+H2O(l) 2LiOH(aq)
    Alkali metal burn in chlorine gas,Cl2 to form white solid metal chlorides.for example;
    2Na(s)+Cl2(g) 2NaCl(s)
    The reactions between alkali metals and bromine gas,Br2.alkali metals burn in bromine
    gas,Br2 to from metal bromides.for example;
    2K(s)+Br2(g) 2KBr(s)
    Why are the Group 1 Elements so REACTIVE?
    The first three elements in Group 1 are Lithium, Sodium and Potassium and the three pictures
    below show the arrangement of electrons in their atoms.
    They have all got one electron in the outside shell even though they all have a different number
    of electrons in total. If you compare these pictures with the periodic table, above, you might
    notice that the elements have more electrons as you go down the the group.

    Lithium Sodium Potassium


    The chemical propertietheir
    electron arrangements of atoms
    Alkali metals have one electron in their outermost occupied shells.each of them reacts by
    donating one electron from its outermost occupied shell to from its outermost occupied
    shell to form an ion with a charge of+1,thus achieving the stable electron arrangement of
    the atom of noble gas.
    Alkali metal Electron arrangement

    lithium(Li) 2.1

    Sodium(Na) 2.8.1

    Potassium(K) 2.8.8.1

    Rubidium(Rb) 2.8.18.8.1

    Caesium(Cs) 2.8.18.18. 8.1

    francium(Fr) 2.8.18.32.18.8.1
    The safery precautions to betaken when handling
    group 1 elements
    All alkali metals are extremely reactive. Lithium,sodium,and potassium must be stored in
    paraffin oil in bottles.safety precautions must be taken when handing alkali metals.

     Do hold alkali with your bare hands.


     Use forceps to take them and remember to wear safety goggles and gloves.
     When conducting experiments,make sure that only a small piece of alkali metal is used.
    Bye-bye………………………..

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