Q.3.Comment on the trend in the chemical reactivity in a period and in groups(1 & 17) of the modern periodic table.
Answers
Explanation:
The vertical columns in the periodic table of the elements are known as groups.
Group 17 elements lie in the second last column from the right of the periodic table.
Elements in Group 17 are:
Group 17 Elements
(Halogens)
Name Symbol
fluorine F
chlorine Cl
bromine Br
iodine I
astatine (1) At
Group 17 elements are also known as:
(a) halogens(2) (name still in common use)
(b) Group VIIA (name no longer used)
Group 17 elements are non-metals
Group 17 elements exist as diatomic molecules (X2) when not combined with other elements.
Group 17 elements can combine with nearly all the elements in the periodic table. These compounds can be:
(i) ionic (eg, metal + halogen → metal halide)
(ii) covalent (eg, non-metal + halogen → non-metal halide)
All Group 17 (group VIIA or halogen) elements have 7 valence electrons (7 electrons in the valence shell or highest energy level).
Atomic radius increases down Group 17 from top to bottom.
Electronegativity decreases down group 17 from top to bottom.
Chemical reactivity of group 17 elements decreases down group 17 from top to bottom.
First ionization energy decreases down group 17 from top to bottom.
Melting point and boiling point increase down Group 17 from top to bottom.
Elements become darker in colour going down group 17 from top to bottom.
Metallic character of the group 17 elements increases down the group from top to bottom.
Summary of trends in the properties of Group 17 elements is shown below:
Increasing Trend: Name Decreasing Trend:
Atomic Radius Melting Point Metallic Character Reactivity Electronegativity First Ionisation Energy
smallest lowest least metallic fluorine most reactive largest highest
↓ ↓ ↓ chlorine ↑ ↑ ↑
↓ ↓ ↓ bromine ↑ ↑ ↑
largest highest most metallic iodine least reactive