Question

1. describe the trends in melting point of group 1 elements
2. describe the trends in density for the group 1 elements
3. define groups on the periodic table

Answer 1

1. Generally the melting point of the alkali metals decreases down the group. This is because as the ions get larger the distance between the bonding electrons and the positive nucleus gets larger and reduces the overall attraction between the two. For similar reasons the electronegativity decreases.

2. Trends in Density

The densities of the Group 1 elements increase down the group (except for a downward fluctuation at potassium). ... The metals in this series are relatively light—lithium, sodium, and potassium are less dense than water (less than 1 g cm-3).

3. Group, in chemistry, a column in the periodic table of the chemical elements. In a group, the chemical elements have atoms with identical valence electron counts and identical valence vacancy counts. This similarity in both the composition and structure of their atomic valence shells implies a corresponding similarity in both their chemical and physical properties. Groups are numbered from 1 to 18. From left to right in the periodic table, there are two groups (1 and 2) of elements in the s-block, or hydrogen block, of the periodic table; ten groups (3 through 12) in the d-block, or transition block; and six groups (13 through 18) in the p-block, or main block. The elements in the f-block, or inner-transition block, the lanthanoids and actinoids, are not given group numbers.

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Answer 2

1. Trends in melting point of Group 1 elements:

• The melting point across Group 1 elements decreases down the group due to the fact of increase in size of elements.

• Larger the size of metal ions , lower is their melting point due to less electrostatic force of attraction between the nucleus and the outer shell.

2. Trends in density for Group 1 elements:

• Larger the size of metal ion, higher is the density.

• Hence, density across Group 1 increases as we move down.

3. Define groups across a periodic table:

• Groups in a periodic table is acolumn having chemical elements with same valence electrons.
• There are total 18 groups in a periodic table.
• GROUP 1 elements are called as Alkali Metals while, GROUP 2  elements are called as Alkali Earth Metals.
• Elements from Group 4 to 12 are called as Transition Metals
• Elements of GROUP 13 are called as Boron Fmily while of GROUP 14 are called as Carbon family.
• Elements of GROUP 15 are called Nitrogen family , while of GROUP 16 are called Oxygen Family.
• GROUP 17 elements are called Halogens and Group 18 elements are called as Noble  Gases.
• Each group has their specific properties they exhibit with different trends.