Chemistry

The chemical bonds can be primary or strong bonds such as ionic, covalent, and metallic bonds. It can also be the secondary or weak bonds like hydrogen bonding, London dispersion force, and dipole interactions.

It is the bond that holds the ions, atoms or molecules to form stable substances, compounds and larger structures.

In Chemistry, the bonds are of four types - Covalent bond, Ionic bond, Hydrogen bond, and Metallic bond.

Applying conservation of momentum for collision of blocks

$2mv+0=3m{v}^{\text{'}}$

$?v^{\text{'}}=\frac{2v}{3}\dots \left(1\right)$

Now, from conservation of energy

$\frac{1}{2}*3m*{v^{\text{'}}}^2=\frac{1}{2}k{x}_0^2$

$x_0=\sqrt[]{\frac{3m{v}^{\text{'}2}}{k}}=v\text{'}\sqrt[]{\frac{3m}{k}}$

$=\frac{2v}{3}\sqrt[]{\frac{3m}{k}}=v\sqrt[]{\frac{4m}{3k}}$

Angular momentum imparted to sprinkler per

$second=vr\frac{dm}{dt}=\frac{0.6}{60}*0.5*1=0.005N.m$

$?l\frac{d\omega }{dt}=0.005$

$?\frac{d\omega }{dt}=\frac{0.005}{500*{10}^{-7}}$

$=100\frac{rad}{s^2}$

For normal emergence

$r=A$

From Snell's Law

$\frac{\sin ?i}{\sin ?r}=\frac{\mu }{1}$

$?\sin ?i=\sqrt[]{2}\sin ?{30}^0$

$?i={45}^0$

You can read the classification of elements and periodicity in properties class 11 notes to study class 11 ch3 and score well in class 11th exams and NEET, and JEE exams.

When the elements having similar properties repeat at regular intervals, it is called periodicity in the properties of elements.

Classification of Elements is Necessary because it helps in understanding and remembering elements' properties better, you can understand how elements react or behave, and can guess properties of unidentified or newly discovered elements.

Yes, one can see the atoms, but not with the naked eye. One needs to use specialised microscopes to see the atoms. To see the atoms, one can use electron microscopes such as electron ptychography and TEM, or they can also use Scanning Tunneling Microscope (STM).