CHEMISTRY [2 Mark Question Answer]

to get inert gases first write configuration with help of atomic number = number of proton
P 6= 2,4
Q18=2,8,8
R17= 2,8,7
S9=2,7
Hence Q is only inert due to octet rules

Chlorine atom has more energy because it is unstable ! More unstable a molecuke or an atom is, the more energy it has . And so Cl2 has less energy than Cl as Cl2 is highly stable and can be found in a free state in the nature!

(a) a duplet structure -Helium is the only noble gas which has only two electrons in its valence shell. Such an electronic configuration of a valence shell is called duplet structure
(b) an octet structure:- all noble gases, has a full valence shell. Noble gases have eight electrons in their outermost shell, except in the case of helium, which has two

(a) inert gases
(b) The atoms of noble gases already have complete outer shells, so they have no tendency to lose, gain, or share electrons. This is why the noble gases are inert and do not take part in chemical reactions
(c) Their outermost shell is incomplete. They can lose, gain or share electrons. Thus they are chemically reactive.

(a) They have similar chemical properties because isotopes of an element have the same number of electrons as an atom of that element. The electron arrangement is the same owing to same chemical properties
(b) In every isotope the charged subatomic particles which are protons and electrons are in equal number. Thus, an isotope is electrically neutral. Note: In every isotope there will be an equal number of electrons and protons

(a) electronic configuration of A is = 2,8,8
(b) electronic configuration of B is= 2,8,8,2
(c) No Isotope due to deferent atomic number
(d) B is metal

The atomic masses of most elements are fractional because they exist as a mixture of isotopes of different masses. Since the atomic mass of isotopes are different, so average atomic mass is calculated for a single element.

They have similar chemical properties because isotopes of an element have the same number of electrons as an atom of that element. The electron arrangement is the same owing to same chemical properties. However they have different numbers of neutrons, which affects the mass number

The reason for the existence of isotopes is a change in (c) neutron number. A given element can have different isotopes owing to the difference in the number of neutrons but the number of protons and electrons remains the same.

An isotope is one of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behavior but with different atomic masses and physical properties. Every chemical element has one or more isotopes.

we know that chemical properties depend upon number of valence electron hence first find out valence electron
A3=2,1,
B9=2,7
C11=2,8,1
D17 = 2,8,7
Therefore Element A, C and B, D are two pair
A,C pair is metallic

(a) number of valence electrons in P, Q and R is 2, 2, 2 respectively
(b) similar chemical properties?
(c) these elements metals

(a) Self
(b) Self
(c ) Self

Atomic number =20
Electronic configuration = 2, 8, 8, 2
Name the shell which has valence electrons= N shell
and the number of valence electrons in it.= 2

(a) The electrons present in the valence shell are called valence electrons
(b) Because these outer shell electrons are responsible in chemical bonding

2,8,5

2,8,8,1

2,4

2,8,8,7

(a) Self
(b) Self
(c) Self
(d) Self

Electronic configuration is the arrangement of electrons around the nucleus of a particular atom or molecule. An atom is made of tiny particles called protons, neutrons, and electrons. A neutral atom has the same number of protons and elections
The rule of the Bohr-Bury Scheme can be stated as follows: -The electrons in the atom are arranged around the nucleus in different shells and the electrons first occupy that shell which is closest to the nucleus as it has the lowest energy. -The second shell is called the L-shell which can take upto eight electrons.

A neutron is a subatomic particle found in the nucleus of every atom except that of simple hydrogen. The particle derives its name from the fact that it has no electrical charge; it is neutral. Neutrons are extremely dense.

The electrons in an atom are arranged in shells that surround the nucleus, with each successive shell being farther from the nucleus.
(a) nearest to nucleus called bound shell
(b) farthest from nucleus called valence shell

According to Bohr Atomic model, a small positively charged nucleus is surrounded by revolving negatively charged electrons in fixed orbits. He concluded that electron will have more energy if it is located away from the nucleus whereas the electrons will have less energy if it located near the nucleus

Rutherford’s atomic model failed to explain the stability of electrons in a circular path. He stated that electrons revolve around the nucleus in a circular path, but particles in motion would undergo acceleration and cause energy radiation.

(a) Rutherford and the Discovery of the Atomic Nucleus. In 1909
(b) Rutherford’s gold foil experiment showed that the atom is mostly empty space with a tiny, dense, positively-charged nucleus. Based on these results, Rutherford proposed the nuclear model of the atom

an atom is made up of a positively charged sphere into which negatively charged electrons are implanted. Because electrons and protons have the same magnitude, an atom as a whole is electrically neutral

three properties of positive rays

• (i) They travel in straight lines and cast shadows of objects placed in their path. …
• (ii) They are deflected by electric and magnetic fields but the deflections are small as compared to that of cathode rays.
• (iii) They are the streams of positive ions of the gas enclosed in the discharge tube.