(a) What is a period in a periodic table? How do atomic structures (electron arrangements) change in a period with increase in atomic numbers from left to right?
(b) How do the following change on going from left to right in a period of the periodic table?
(i) Chemical reactivity of elements (ii) Nature of oxides of elements
Give examples in support of your answer.
(a) A period is a horizontal row of elements in a periodic table.
As the atomic number increases from left to right, the size of the atom increases.
(b)(i) On moving from left to right in a period of the periodic table, the chemical reactivity first decreases and then increases.
Example: In the 3rd period of elements, sodium is a very reactive element, magnesium is less reactive whereas aluminium is still less reactive. Silicon is the least reactive in the third period. Now, phosphorus is quite reactive, sulphur is still more reactive whereas chlorine is very reactive. Therefore, the reactivity of the elements first decreases and then increases along the period.
(ii) The basic nature of oxides decreases whereas the acidic nature of oxides increases from left to right in a period
Example: In the 3rd period of the periodic table, sodium oxide is highly basic in nature and magnesium oxide is comparatively less basic. The aluminium and silicon oxides are amphoteric in nature. Phosphorus oxides are acidic, sulphur oxides are more acidic whereas chlorine oxides are highly acidic. Thus, the basic nature of the oxides decreases whereas the acidic nature of oxides increases along the period.
Related Articles
- How do the atomic radii of elements change as we go from left to right in a period of the periodic table?
- How do electronic configurations of elements change in second period of periodic table with increase in atomic numbers?
- How does the valency of elements change on moving from left to right in the third period of the periodic table?
- (a) How does the size of atoms (atomic size) generally vary in going from left to right in a period of the periodic table? Why does it vary this way?(b) What happens to the metallic character of the elements as we move from left to right in a period of the periodic table?
- How would the tendency to gain electrons change on moving from left to right in a period of the periodic table?
- How does the metallic character of elements change along a period of the periodic table from the left to the right and why?
- How does the number of valence electrons vary on moving from left to right:(i) In the first period of the periodic table? (ii) In the second period of the periodic table?
- (a) How does the electropositive character of elements change on going down in a group of the periodic table?(b) State how the valency of elements varies (i) in a group, and (ii) in a period, of the periodic table.
- How would the tendency to lose electrons change as we go from left to right across a period of the periodic table?
- (a) List any three observations which posed a challenge to Mendeleev’s Periodic law.(b) How does the metallic character of elements vary on moving from(i) left to right in a period,(ii) from top to bottom in a group of the Modem Periodic Table?Give a reason for your answer.
- On moving from left to right in a period in the periodic table, the size of the atom.increasesdecreasesdoes not change appreciablyfirst decreases and then increases/p>
- What is periodicity in properties of elements with reference to the Modern Periodic Table? Why do all the elements of the same group have similar properties? How does the tendency of elements to gain electrons change as we move from left to right in a period? State the reason of this change?
- (a) What is the main characteristic of the last elements in the periods of the periodic table? What is the general name of such elements?(b) What is the number of elements in: (a) 1st period, and (b) 3rd period, of the modern periodic table?
- (a) Explain why:(i) All the elements of a group have similar chemical properties. (ii) All the elements of a period have different chemical properties. (b) The atomic radii of three elements X, Y, and Z of a period of the periodic table are 186 pm; 104 pm, and 143 pm respectively. Giving a reason, arrange these elements in the increasing order of atomic numbers in the period.
- (a) What is meant by (i) a group, and (ii) a period, in a periodic table?(b) How many periods and groups are there in the long form of periodic table? (c) Give two examples each of (i) group 1 elements (ii) group 17 elements (iii) group 18 elements.
Kickstart Your Career
Get certified by completing the course
Get Started