1)The modern Periodic Table is arranged in order of increasing atomic number. As one moves from one element to another on the right, one more proton is found in the nucleus, and one more electron is found in the same electron 'shell' (energy level). For this reason, all the elements in Period 3 have the first electron 'shell' (energy level) filled with 2 electrons and the second electron 'shell' (energy level) filled with 8 electrons (the electronic configuration of Neon).
For example,Sodium begins a new electron 'shell' ( 3rdenergy level) with 1 electron, Magnesium has 2 electrons in the third electron 'shell' (energy level), Aluminium has 3 electrons in the third electron 'shell' (energy level) etc, until finally the third electron 'shell' (energy level) is filled with 8 electrons and the stable electronic configuration of the Noble Gas Argon is reached (2,8,8).
2)ATOMIC RADII:
Atomic radius of the elements decrease across the Period from left to right. As we move from left to right across the period one more proton is added to the nucleus of each successive atom, and one more electron is added to the same electron 'shell' (energy level) of each successive atom. The increased positive charge in the nucleus of each successive atom attracts all the electrons in the atom more strongly, so they are drawn in more closely towards the nucleus.
3)1st Ionization Energy :
1st Ionization Energy (the energy required to remove an electron from the gaseous atom) increases across the Period from left to right. The further away from the positively charged nucleus that a negatively charged electron is, the less strongly the electron is attracted to the nucleus and so the more easily that electron can be removed. So, as the atomic radius decreases from left to right across the Period so the 1st Ionization Energy increases.
4)Electronegativity :
Electronegativity(the relative tendency shown by an atom to attract electrons to itself) increases across the Period from left to right. Typically, metals have low electronegativity, little ability to attract electrons, while non-metals have high electronegativity, greater ability to attract electrons. As we move from left to right across the Period, the elements become less metallic in nature (more non-metallic).
2.8.09
Relative trend in melting point of period 3 elements.Explain.
1)MELTING AND BOLING POINT:
a)Melting
When a substance melts, some of the attractive forces holding the particles together are broken or loosened so that the particles can move freely around each other but are still close together. The stronger these forces are, the more energy is needed to overcome them and the higher the melting temperature.
b)Boiling
When a substance boils, most of the remaining attractive forces are broken so the particles can move freely and far apart. The stronger the attractive forces are, the more energy is needed to overcome them and the higher the boiling temperature.
-Sodium, magnesium and aluminium
Sodium, magnesium and aluminium are all metals. They have metallic bonding, in which positive metal ions are attracted to delocalised electrons. Going from sodium to aluminium:
The charge on the metal ions increases from +1 to +3 (with magnesium at +2),
the number of delocalised electrons increases, so the strength of the metallic bonding increases and
the melting points and boiling points increase.
i)Silicon
Silicon is a metalloid (an element with some of the properties of metals and some of the properties of non-metals). Silicon has giant covalent bonding. It has a giant lattice structure similar to that of diamond, in which each silicon atom is covalently-bonded to four other silicon atoms in a tetrahedral arrangement. This extends in three dimensions to form a giant molecule or macromolecule.
Silicon has a very high melting point and boiling point because all the silicon atoms are held together by strong covalent bonds which need a very large amount of energy to be broken.
ii)Phosphorus, sulphur, chlorine and argon
These are all non-metals, and they exist as small, separate molecules. Phosphorus, sulphur and chlorine exist as simple molecules, with strong covalent bonds between their atoms. Argon exists as separate atoms (it is monatomic).
Their melting and boiling points are very low because:
When these four substances melt or boil, it is the van der Waals’ forces between the molecules which are broken ...
which are very weak bonds thus little energy is needed to overcome them.
Sulphur has a higher melting point and boiling point than the other three because:
phosphorus exists as P4 molecules,sulphur exists as S8 molecules, chlorine exists as Cl2 molecules and
argon exists individual Ar atoms.
The strength of the van der Waals’ forces decreases as the size of the molecule decreases
so the melting points and boiling points decrease in the order S8 > P4 > Cl2 > Ar.
a)Melting
When a substance melts, some of the attractive forces holding the particles together are broken or loosened so that the particles can move freely around each other but are still close together. The stronger these forces are, the more energy is needed to overcome them and the higher the melting temperature.
b)Boiling
When a substance boils, most of the remaining attractive forces are broken so the particles can move freely and far apart. The stronger the attractive forces are, the more energy is needed to overcome them and the higher the boiling temperature.
-Sodium, magnesium and aluminium
Sodium, magnesium and aluminium are all metals. They have metallic bonding, in which positive metal ions are attracted to delocalised electrons. Going from sodium to aluminium:
The charge on the metal ions increases from +1 to +3 (with magnesium at +2),
the number of delocalised electrons increases, so the strength of the metallic bonding increases and
the melting points and boiling points increase.
i)Silicon
Silicon is a metalloid (an element with some of the properties of metals and some of the properties of non-metals). Silicon has giant covalent bonding. It has a giant lattice structure similar to that of diamond, in which each silicon atom is covalently-bonded to four other silicon atoms in a tetrahedral arrangement. This extends in three dimensions to form a giant molecule or macromolecule.
Silicon has a very high melting point and boiling point because all the silicon atoms are held together by strong covalent bonds which need a very large amount of energy to be broken.
ii)Phosphorus, sulphur, chlorine and argon
These are all non-metals, and they exist as small, separate molecules. Phosphorus, sulphur and chlorine exist as simple molecules, with strong covalent bonds between their atoms. Argon exists as separate atoms (it is monatomic).
Their melting and boiling points are very low because:
When these four substances melt or boil, it is the van der Waals’ forces between the molecules which are broken ...
which are very weak bonds thus little energy is needed to overcome them.
Sulphur has a higher melting point and boiling point than the other three because:
phosphorus exists as P4 molecules,sulphur exists as S8 molecules, chlorine exists as Cl2 molecules and
argon exists individual Ar atoms.
The strength of the van der Waals’ forces decreases as the size of the molecule decreases
so the melting points and boiling points decrease in the order S8 > P4 > Cl2 > Ar.
Subscribe to:
Posts (Atom)
.JPG)