The correct answer is Monoatomic. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Very little reactivity. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is He. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Noble non-metals. Group 1 elements, known as alkali metals, are highly reactive, electropositive metals that readily lose one electron to form a +1 ion.

The correct answer is NiCl₂. Transition elements (groups 3-12) are characterized by the filling of d-orbitals. They are all metals, often act as excellent catalysts, and frequently form coloured compounds.

The correct answer is Ni. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Fe. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Metals. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Transition elements. Group 1 elements, known as alkali metals, are highly reactive, electropositive metals that readily lose one electron to form a +1 ion.

The correct answer is Both a and b. Transition elements (groups 3-12) are characterized by the filling of d-orbitals. They are all metals, often act as excellent catalysts, and frequently form coloured compounds.

The correct answer is Transition metals. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is First group. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Cl₂. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Pale yellow. Elements within the same group share similar chemical properties and exhibit distinct periodic trends in their physical and chemical behavior.

The correct answer is HF. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Increase in a group. Group 17 elements, known as halogens, are highly electronegative non-metals that typically exist as diatomic molecules and readily gain one electron to form a -1 ion.

The correct answer is Reduction. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Cl₂. Group 17 elements, known as halogens, are highly electronegative non-metals that typically exist as diatomic molecules and readily gain one electron to form a -1 ion.

The correct answer is Diatomic molecules. Group 17 elements, known as halogens, are highly electronegative non-metals that typically exist as diatomic molecules and readily gain one electron to form a -1 ion.

The correct answer is Nitrogen. Group 1 elements, known as alkali metals, are highly reactive, electropositive metals that readily lose one electron to form a +1 ion.

The correct answer is HF. Elements within the same group share similar chemical properties and exhibit distinct periodic trends in their physical and chemical behavior.

The correct answer is Halogens. Group 1 elements, known as alkali metals, are highly reactive, electropositive metals that readily lose one electron to form a +1 ion.

The correct answer is Fluorine. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Basic in nature. As a general periodic trend, metal oxides are basic in nature, while non-metal oxides tend to be acidic.

The correct answer is Acidic in nature. As a general periodic trend, metal oxides are basic in nature, while non-metal oxides tend to be acidic.

The correct answer is Negative ion. Elements within the same group share similar chemical properties and exhibit distinct periodic trends in their physical and chemical behavior.

The correct answer is Mercury. These physical properties distinguish specific elements or groups; for example, alkali metals are soft, mercury is a liquid metal at room temperature, and diamond is an exceptionally hard non-metal.

The correct answer is All of these. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Diamond. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Selenium. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Na₂O. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is HI. Group 17 elements, known as halogens, are highly electronegative non-metals that typically exist as diatomic molecules and readily gain one electron to form a -1 ion.

The correct answer is 180°C. Group 1 elements, known as alkali metals, are highly reactive, electropositive metals that readily lose one electron to form a +1 ion.

The correct answer is Similar chemical properties. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Li. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is K. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Alkali metals. Group 1 elements, known as alkali metals, are highly reactive, electropositive metals that readily lose one electron to form a +1 ion.

The correct answer is They are electropositive. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Sodium. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Lithium. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.

The correct answer is Nitrogen. Group 1 elements, known as alkali metals, are highly reactive, electropositive metals that readily lose one electron to form a +1 ion.

The correct answer is Fourth group. Transition elements (groups 3-12) are characterized by the filling of d-orbitals. They are all metals, often act as excellent catalysts, and frequently form coloured compounds.

The correct answer is Ba. Group 18 elements are noble gases. They are monoatomic, have completely filled valence shells (like the stable duplet of Helium), and exhibit very little chemical reactivity.