Question

An element Barium has atomic number 56. Look up its position in the Periodic Table and answer the following questions.
(i) Is it a metal or a non-metal?
(ii) Is it more or less reactive than calcium?
(iii) What is its valency?
(iv) What will be the formula of its phosphate?
(v) Is it larger or smaller than cesium (Cs) in size?

Answer 1

Barium is a chemical element (symbol Ba) with atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. This question can be solved with reference to the position of the barium.

Complete Solution :
Let's discuss each question one by one and find their answers:
Answer (i)- Metallic character implies the level of reactivity of a metal. Metals tend to lose electrons in chemical reactions due to their low ionization energies. The metallic character increases as we go down a group. It is irrelevant with going along a period in a periodic table. Therefore, barium (Ba) is a metal.
Answer (ii)- Reactivity refers to how likely or vigorously an atom reacts with other substances. This is usually determined by how easily electrons can be removed and how badly they want to take other atom's electrons (electronegativity) because it is the transfer of electrons that is the basis of chemical reactions. For metals reactivity decreases as you go from left to right across a period and reactivity increases as you go down a group. Therefore, Ba is less reactive than Cs.
Answer (iii)- Barium (Ba) is an alkaline earth metal that has 2 outer shells. Like the other metals in this group, it readily loses these electrons to form a $B{a^{2 + }}$ ion. So, barium has a valency of 2 which is the same if we go down the group with some exceptions.
Answer (iv)- Barium phosphate is an inorganic salt consisting of 3 cations and 2 anions. The cation is of barium ($B{a^{2 + }}$) and the anion is phosphate ($P{{O_4}^{2 - }}$). The chemical or molecular formula of Barium phosphate is $B{a_3}{(P{O_4})_2}$.
Answer (v)- The size of neutral atoms is drawn from the atomic radius, which is half the distance between two atoms which are just touching each other. As you move down an element group (column), the size of atoms increases. This is because each atom further down the column has more protons and neutrons and also gains an additional electron energy shell. Therefore, cesium (Cs) is larger in size than barium (Ba).

Note: In order to solve these kinds of questions, you must memorize the trend of metallic character, electronegativity, atomic size, atomic radius etc. along the periodic table.