Valency and Oxidation states

Q. Why oxidation number of oxygen in hydrogen peroxide is -1 not -2 ? Explain with diagram.

Q. How does the reactivity of nonmetals very down a group?

Q.

What is the most common oxidation state for actinoids?

Q.

Name the element with the electronic configuration 2, 8, 8, 1.

1. Francium

2. Caesium

3. Potassium

4. Sodium

Q.

Valency of an element depends upon the number of shells in an atom.

1. Ture

2. False

Q.

The oxidation number of carbon in diamond is:

1. Zero

2. $+4$

3. $-4$

4. $+2$

Q.

Which is more reactive manganese or aluminium?

Q. Give the number of the group and the period of the element having three shells with three electrons in valence shell.

Q.

Choose the word or phrase from the brackets which correctly completes each of the following statements:-

(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 from left to right in a given period, the number of shells ...... (remains the same/ increases decreases).

(c) On moving down a group, the number of valence electrons ....... (remains the same/increases/decreases).

(d) Metals are good ............. (oxidising agent/ reducing agent) because they are electron.......... (acceptors/donors).

Q.

Metals are good …….. (Oxidizing agents/reducing agents) because they are electron….…. (Acceptors/donors).

Q.

Element M forms a chloride with the formula $MC{l}_2$ which is a solid with high melting point. M would most likely be in the group in which .................. is placed.

[(a) Na (b) Mg (c) Al (d) Si. ]

Q.

Show the formation of lithium ion.(Atomic number of Li = 3)

Q.

A species 'X' contains 9 protons, 10 electrons and 11 neutrons. It is

1. A neutral atom

2. An isotope

3. A cation

4. An anion

Q.

Write the symbol and valency for the following radical:

Silicate

Q.

The chemical symbol for Bromine is Br.

1. True
2. False

Q.

The number of nucleons in a normal carbon atom is _____.

Q. Which of the following element needs only one electron to attain noble gas configuration?

1. Sodium
2. Oxygen
3. Chlorine
4. Neon

Q.

Which of the following halogens doesn't exhibit positive oxidation state in its compounds?

1. Br

2. I

3. F

4. Cl

Q. What is the common oxidation state of all the elements of alkali metals, halogens and noble gases?

Q.

How to count the oxidation number of NH₄⁺ N₂H₄ NH₂OH and N₂O?

Q.

Give the name and symbol of element which occupies in period 3 and group zero.

Q.

Name a trivalent cation with its formulae and valency.

Q.

The valency of phosphate ion is ____.

Q.

$\left(\mathrm{a}\right)$Electropositive nature of the element(s) increases down the group and decreases across the period

$\left(\mathrm{b}\right)$Electronegativity of the element decreases down the group and increases across the period

$\left(\mathrm{c}\right)$Atomic size increases down the group and decreases across a period (left to right)

$\left(\mathrm{d}\right)$ Metallic character increases down the group and decreases across a period.

Based on the above trends of the periodic table, answer the following about the elements with atomic numbers $3$ to $9$. Name the element which shows maximum valency.

Q.

The element A and B have an electronic configuration (2, 8, 18, 2) and (2, 6) respectively.

(1)To which period do A and B belong?

(2)To which groups A and B belong?

Q. Identify the elements with seven valence electrons.

1. Bromine
2. Phosphorus
3. Nitrogen
4. Chlorine
5. Calcium
6. Helium
7. Iodine
8. Astatine
9. Fluorine

Q.

The atom of an element has 9 protons, 9 electrons, and 10 neutrons. Predict the valency of the element.

Q. What is a lone pair of electrons?

1. A pair of electrons which is shared by the reacting atoms is called a lone pair of electrons.

2. A pair of electrons which is lost by one of the reacting atoms is called a lone pair of electrons.

3. A pair of electrons which is gained by one of the reacting atoms is called a lone pair of electrons.

4. A pair of electrons which is not shared by any of the reacting atoms is called a lone pair of electrons.

Q.

Given below are the electronic configurations of some elements:

(a) 2, 8, 3

(b) 2, 8, 18, 5

(c) 2, 8, 7

(d) 2, 8, 18, 8, 1

(e) 2, 8, 2

(f) 2, 5

(g) 2, 8, 18, 8

Answer the following:

(f) which elements belong to the same group?

Q.

Element X forms a chloride with the formula XCl₂, which is a solid with high melting point. X would most likely be:

1. Si

2. Mg

3. Na

4. Al