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Atomic radius is an example of a physical property that shows a periodic trend within the alkali metal group. Other physical properties such as density, melting point, and boiling point also show trends within this group. The table below shows data for the first 3 alkali metals including atomic radius, density, melting point, and boiling point.
Atomic radius is an example of a physical property that shows a periodic trend within the alkali metal group. Other physical properties such as density, melting point, and boiling point also show trends within this group. The table below shows data for the first 3 alkali metals including atomic radius, density, melting point, and boiling point.
Table 5: Physical properties of the alkali metal elements
Atomic radius is a measure of the physical size of an atom. In general, atomic radius tends to increase as the number of energy levels containing electrons increases. As a result, you see a trend of increasing atomic radius as you move down within a group.
Density is the mass per unit volume of a substance. It is usually measured in g/cm3. The observed trend in density is influenced by two factors. More protons and neutrons are present in an atom’s nucleus as you move down within a group, which increases both the positive charge of the nucleus of that atom and the mass of the atom. As protons are added, mass increases, but the electrons are pulled closer to the nucleus by the stronger positive charge of the increasing number of protons. Volume does not increase as much as mass increases, and so density tends to increase. This is not a consistent trend, as you can see by comparing the densities of sodium and potassium.
Melting point and boiling point are properties that also display group trends within the alkali metals. Both of these properties are influenced by the strength of the attractive forces between atoms. Smaller atoms experience stronger attractive forces because of the smaller distance between the positively charged nucleus of one atom and the negatively charged electrons of an adjacent atom. Thus, it takes more energy, provided by higher temperatures, to melt solids composed of small atoms than to melt solids composed of large atoms. Likewise, more energy must be used to vaporize liquids composed of small atoms than liquids composed of large atoms. This explains why the melting point and the boiling point decrease as you go down within the group.
Knowing that the increasing order of the radius of group 1 elements is Li < Na < K < Rb < Cs.
What is the increasing order of density of group 1 elements?
Cs < Rb < K < Na < Li
Rb < K < Na < Li < Cs
Li < Na < K < Rb < Cs
Na < Li < K < Rb < Cs
answer :
Li < Na < K < Rb < Cs
Knowing that the increasing order of the radius of group 1 elements is Li < Na < K < Rb < Cs.
What is the increasing order of the melting point of group 1 elements?
Cs < Rb < K < Na < Li
Na < Li < K < Rb < Cs
K < Na < Li < Rb < Cs
answer :
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