Periodic Classification of Elements Test - 12

According to the periodic law, when the elements are arranged in the increasing order of their atomic numbers, their properties show periodicity.

$B{r}^{+} < Br < B{r}^{-}$

$B{r}^{-}$ will have the largest atomic size because $B{r}^{-}$ has one extra electron in its valence shell which due to its unbalanced negative charge will be repelled and hence the atomic radius of $B{r}^{-}$ will increase.

In the case of $B{r}^{+}$, the extra positive charge will attract the valence electrons strongly and hence the atomic radius will decrease. 

$Br$ will be intermediate in between $B{r}^{-}$ and $B{r}^{+}$.

Hence, the correct option is (B).

In the modern periodic table, the elements of a group have similar properties because they have the same number of valence electrons.

As we move from top to bottom in a group, the ionization potential decreases due to an increase in size and from left to right in a period, ionization potential increases due to a decrease in size.

As the elements Hydrogen, Lithium and Sodium are from the same group. Moving from hydrogen to Sodium size increases and ionization potential decreases. So Sodium has the least ionization potential.

Hence, the correct option is (C).

The hydroxide of the element belonging to period 3 and group 13 will be amphoteric in nature. The hydroxide will be $Al{\left(OH\right)}_3$ which shows both acidic and basic nature that is why it is amphoteric in nature.

Cl > S > Al > Na

As we move from left to right in a period the size of the elements decreases due to an increase in effective nuclear charge which tends to increase the ionization potential as attractive forces increase which results the requirement of more energy to remove the electron from outermost cell.

Hence, the correct option is (D).

In the same period or group, there is a gradation in a particular property because there is a gradual change in the electronic configuration of the elements. 

In 1865, an English chemist, John Alexander Newland observed that when the lighter elements were arranged in order of their increasing atomic masses, the properties of every 8th elements were similar to those of the first one like the eighth note of a musical scale. This relation is called Newland’s law of octaves.

Element found in a group of periodic table = Group 1

Group 1 elements (Alkali metals) have low density and melting point. They react with cold water vigorously and catch fire.

Hence, the correct option is (A).

Elements with stable configuration, e.g. neon, have an electron affinity value of 0.

The electronegativity values of three elements 'X', 'Y' and 'Z' are 0.93, 2.6, and 3.2, respectively. The chemical bond formed between the atoms 'X' and 'Z' will be electrovalent and the chemical bond formed between 'Y' and 'Z' will be covalent. Because the electronegativity difference between X and Z is high so the X-Z bond will be electrovalent (ionic) while the electronegativity difference between Y and Z is low so the Y-Z bond will be covalent.

Hence, the correct option is (C).

Potassium (Z = 19)

All four elements except Potassium are from the third period. Potassium is an odd one because it is an element of the fourth period.

Hence, the correct option is (D).

Highly non-metallic =B

From the given atomic numbers we can clearly name the elements of the respective atomic number. As atomic numbers $14, 17, 18$, and $19$ are Carbon, Chlorine, Argon, and Potassium respectively. Among these four elements, Potassium is a metal. The rest three are non-metals. Although in a period on going from left to right non-metallic character increases. So Argon should be highly non-metallic but Chlorine is highly non-metallic in nature.

Hence, the correct option is (C).

The proton number of 'A' = 8 less than that of 'B'

Element A is Be (Atomic number =4) and element B is Mg (Atomic number=12).

Since the atomic number of an element is equal to the number of protons in that atom. It is clear from an atomic number that the proton number of A is 8 less than that of B.

F < O < N < B

As we move from left to right in a period, the incoming electron enters in the same outermost shell. The atomic number increases within the same period while moving from left to right which in turn increases the effective nuclear charge. The increase in attractive forces reduces the atomic radius of the elements.

Hence, the correct option is (A).