Chemistry
Assertion (A): Atomic size increases along a period.
Reason (R): Effective nuclear charge increases with atomic number.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Periodic Table
3 Likes
Answer
A is false but R is true.
Explanation — Atomic size decreases across a period (from left to right) in the periodic table. This is because, although electrons are being added, they are added to the same shell, and the increasing effective nuclear charge pulls the electrons closer to the nucleus. Hence, Assertion (A) is false.
As atomic number increases, the number of protons increases, which increases the effective nuclear charge. Hence, Reason (R) is true.
Answered By
2 Likes
Related Questions
Assertion (A): Smaller the size of an atom greater is its electronegativity.
Reason (R): Electronegativity is the tendency of an atom to attract shared pair of electrons towards itself in a molecule.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion (A): Hydrogen is placed in group I.
Reason (R): Hydrogen can gain an electron to achieve noble gas configuration.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Assertion (A): Elements in the same vertical column have similar properties.
Reason (R): Properties depend upon the number of electrons in the valence shell.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is not the correct explanation of A.
- A is true but R is false.
- A is false but R is true.
Fill in the blanks by selecting the correct word from the brackets :
(a) The element below sodium in the same group would be expected to have a …………… (lower/higher) electro-negativity than sodium and the element above chlorine would be expected to have a (lower/higher) ionization potential than chlorine.
(b) On moving down a group, the number of valence electrons …………… (remains the same/increases/ decreases).
(c) Metals are good …………… (oxidising agent/ reducing agent) because they are electron …………… (acceptors/donors).
(d) Down the group, electron affinity …………… [increases, decreases, remains same].
(e) Electronegativity across the period …………… [increases/ decreases].
(f) Non-metallic character down the group …………… [increases/ decreases].
(g) In a period, increase in electron affinity increases …………… (oxidation/reduction).
(h) On descending a group, …………… (increase/decrease) in ionisation potential as well as electron affinity …………… (increases/decreases) oxidising capacity.
(i) If an element has a low ionization energy then it is likely to be …………… (metallic/non metallic).
(j) If an element has seven electrons in its outermost shell then it is likely to have the …………… (largest/smallest) atomic size among all the elements in the same period.