Structure of the Atom — Science STD 9 — Question

Write the distribution of electrons in an atom of element whose atomic number is 18. What is special about the outermost electron shell (or valence shell) of the atom of this element?

Name the scientist who discovered the nucleus of atom.

Name the quantity whose one of the units is Pascal (Pa).

Choose the infrasonic waves and ultrasonic waves from the following frequencies: (i) 10,000Hz (ii) 30,000Hz (iii) 18Hz (iv) 50,000Hz (v) 10Hz

An element X has a valency of 2. Write the simplest formula for:
oxide of the element.

Name the scientists who described the arrangement of electrons in an atom.

What is the value of gravitational constant G (i) on the earth, and (ii) on the moon?

State whether the following statement is true or false:
The symbol of element cobalt is CO.

Compare an electron, a proton and a neutron in respect of their relative masses and charges.

What name has been given to the force with which two objects lying apart attract each other?