Atomic Structure

Bucket 1

100

Rutherford’s alpha-particle scattering experiment was responsible for the discovery of: 

(a) Atomic Nucleus 

(b) Electron

(c) Proton

(d) Neutron 

(c) Proton

200

Helium atom has an atomic mass of 4u and has two protons in it's nucleus. How many neutrons does it have? 

 Ans. 2 neutrons

300

Define Ionization Energy and Electron Affinity.

Ionization Energy of an element is the amount of energy that must be supplied to one mole of the element in the gaseous state to obtain one mole of cations in the gaseous state.

The Electron Affinity is the potential energy change of the atom when an electron is added to a neutral gaseous atom to form a negative ion. 

Bucket 2

100

Atomic number of an element during a chemical    reaction: 

(a) Increases 

(b) Remains Constant

(c) Decreases 

(d) Increases then becomes constant 

(b) Remains Constant

200

If the number of electrons in an atom is 8 and number of protons is also 8, then:

(i) What is the atomic number of the atom? 

(ii) What is the charge on the atom?

i) 8

ii) Neutral

300

Define valency by taking examples of silicon and oxygen.

Ans. Valency: The number of electrons present in an outermost shell or valence electrons which an atom gives or takes or shares in order to complete it's octet or to acquire stable configuration. 

Valency of Sulphur : 2

16=2,8,6 (2 electrons can be gained easily. Hence, valency is 2)

Valency of Oxygen = 2

8=2,6 (2 electrons can be gained easily. Hence, valency is 2)

Bucket 3

100

Atomicity of fluorine is: 

(a) 1 

(b) 2

(c) 3 

(d) 4 

(b) 2

200

If Z=3, what would be the valency of the element? Also, name the element. 

Ans. Valency: 1 

Name of element: Lithium

300

In a gold foil experiment: 

a) Why did many α–particles pass through the gold foil undeflected? 

b) Why did few α–particles deflect through small    angles?

c) Why did few α–particles, after striking the gold    foil, retrace their path?

a) Many α–particles passed through the gold foil undeflected because most of the space inside the atom was empty. 

b) Few α–particles deflected through small angles because there is a positive charge at the center of the gold foil. 

c) Few α–particles, after striking the gold foil, retraced their path, because the positively charged center was concentrated in a very small volume of space and was called nucleus.