Early Atomic Models

What's the size of an electron?

The smallest length scale known in physics is the Planck length. It is an important ingredient in some current cosmological theories. Which of the following expressions could represent this Planck length? (Symbols has usual meaning)

Who gave the first model of an atom?

In an atom ${}_{\text{13}}{\text{AI}}^{\text{27}}$, find the number of neutrons.

In an atom ${}_{\text{13}}{\text{AI}}^{\text{27}}$, find the number of protons.

In an atom ${}_{\text{13}}{\text{AI}}^{\text{27}}$, find the number of electrons.

The gravitational force between a $\mathrm{H}$-atom and another particle of mass $m$ will be given by Newton's law $F=G\frac{M\cdot m}{r^2}$, where $r$ is in metre and

Describe the atomic model of helium atom.

Describe the atomic model of hydrogen atom.

$\alpha$ - particle consists of

G.P. Thomson experimentally confirmed the existence of matter waves by the phenomena of

The number of completely filled shells for the element ${\mathrm{ }}_{16}{\mathrm{S}}^{32}$ is

Consider the following statement:

(I) All isotopes of elements have the same number of neutrons.

(II) Only one isotope of an element can be stable and non-radioactive.

(III) All elements have isotopes.

(IV) All isotopes of Carbon can form chemical compounds with Oxygen$-16$.

The correct option regarding an isotope is:

In 1911, the physical Ernest Rutherford discovered that atoms have a tiny, dense nucleus by shooting positively charged particles at a very thin gold foil. A key physical property which led Rutherford to use gold was that it was

Which of the following properties of atom could be explained correctly by the Thomson Model of atom?

In the experiment for the determination of $\frac{e}{m}$ of electrons by the Thomson method, electric and magnetic fields are

In Thomson's mass spectrographs, when an electric field of $2\times {10}^4 \mathrm{V} {\mathrm{m}}^{-1}$ is applied then the deflection produced on the screen is $20 \mathrm{mm}$. If the length of the plates is $5 \mathrm{cm}$ and the distance of the screen from plates is $21 \mathrm{cm}$ and the velocity of positive ions is ${10}^6 \mathrm{m} {\mathrm{s}}^{-1}$, then their specific charge will be:

In Thomson mass spectrograph, singly and doubly ionised particles from similar parabola corresponding to magnetic fields of 0.8 T and 1.2 T for a constant electric field. The ratio of masses of ionised particles will be