The valency of an element is

Options

A. the mass of the element displacing 1 part by the mass of hydrogen
B. the mass of the element combining with 8 parts by mass of oxygen
C. the number of atoms of hydrogen combin­ ing with 1 atom of the given element
D. the number of atoms in 1 molecule of the given element

Answer

To determine the valency of an element, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Valency**:
- Valency is defined as the combining capacity of an element, which is determined by the number of electrons an atom can lose, gain, or share when it forms chemical bonds.

2. **Identifying Valence Electrons**:
- The valency of an element is closely related to the number of valence electrons in its outermost shell.
- Elements with 1 to 4 valence electrons typically lose electrons to achieve a stable configuration, while those with 5 to 8 valence electrons tend to gain electrons.

3. **Examples of Valency**:
- For example, sodium (Na) has an atomic number of 11 and an electronic configuration of 2, 8, 1. It has 1 valence electron, which it will lose to achieve a stable configuration, giving it a valency of 1.
- Carbon (C), with 4 valence electrons, can neither lose nor gain 4 electrons easily, so it shares electrons with other atoms, resulting in a valency of 4.

4. **Using the Hydrogen Atom**:
- The valency can also be determined by the number of hydrogen atoms that can combine with one atom of the element. For instance, if an element combines with 4 hydrogen atoms, its valency is 4.

5. **Conclusion**:
- Based on the above understanding, we can conclude that the valency of an element can be defined as the number of hydrogen atoms that can combine with one atom of the element, or the number of electrons it can lose or gain.

### Final Answer:
The valency of an element is defined by the number of hydrogen atoms that can combine with one atom of the element or the number of electrons it can lose or gain.