Advertisements
Advertisements
प्रश्न
If an atom ‘A’ has atomic number 19 and mass number 39, state –
- Its electronic configuration.
- The number of valence electrons it possesses.
Advertisements
उत्तर
Atom ‘A’ has mass number A = 39 and atomic number Z = 19 = p
∴ A = Z + n
A = p + n
39 = 19 + n
n = 39 – 19 = 20
But e = p = 19
- A (K, L, M, N)
19 = 2, 8, 8, 1
There will be 2 electrons in K-shell or 1st shell
8 electrons in 2nd shell or L-shell
8 electrons in 3rd shell or M-shell
1 electron in 4th shell or nth-shell - The number of valence electrons i.e. in outer most shell = 1 electron.
APPEARS IN
संबंधित प्रश्न
Name the particles which actually determine the mass of an atom.
Fill in the blank of the following statement :
All the mass of an atom is concentrated in a small region of space called the ___________.
Fill in the following blanks :
| Atomic Number | Mass Number | Protons | Neutrons | Electrons | Symbol |
| 10 | 22 | _________ | _________ | _________ | _________ |
The atom of an element X has 7 electrons in its M shell.
What is the atomic number of element X?
Match the statements in List I with the correct answer from List II.
| List I | List II |
| 1. Mass number of an atom is the number of protons and | A: Electron |
| 2. The sub-atomic particle with a negligible mass. | B: Argon |
| 3. An atom having stable electronic configuration. | C: Nitrogen |
| 4. A molecule formed by sharing of electrons [covalency] | D: Sodium |
| 5. A metallic atom having unstable electronic configuration. | E: Neutrons |
The diagram represents an isotope of hydrogen [H]. Answer the following:
Atomic no. = 1
Mass no. = 1
Which sub-atomic particles in the 3 isotopes of ‘H’ are the same.
From the symbol \[\ce{^4_2He}\] for the element helium, write down the mass number and the atomic number of the element.
Differentiate between the following term:
Atomic number and mass number
Which of the following are true for an element?
- Atomic number = number of protons + number of electrons
- Mass number = number of protons + number of neutrons
- Atomic mass = number of protons = number of neutrons
- Atomic number = number of protons = number of electrons
______ = No. of protons = No. of the electrons.
