Atomic structure

Question 1

Describe an atom?

Answer 1

An atom is the smallest particle that can take place in a chemical reaction independently. It has a small dense nucleus with protons and nuetrons in it and in its surrounding there is empty space where elcetrons are moving

Question 2

what is the charge and mass of electron, proton and nuetron?

Answer 2

Electron : -1 and mass= 1/1836 (taken in terms of nuetron and proton mass)
Proton : +1 and mass= 1
Nuetron : no charge and mass = 1

Question 3

What is proton/atomic number and Nucleon/Mass number? and why is electron mass not considered?

Answer 3

The proton/atomic number is the number of protons in the atom
The nucleon/mass number is the number of protons + number of neutrons in the molecules.

The electron mass is not taken into account as its mass is negligible

Question 4

describe the behaviour of beams of protons, neutrons and electrons moving at the same velocity in an
electric field?

Answer 4

The electron shows deflection to the positive charged plates because opposite charges attract meanwhile the proton shows deflection towards the negative charged plates as opposite charges attract. Nuetron shows no deflection as it has no charge.
The electron deflection is way more in comparison to proton if the beams are struck with the same velocity because the electron is much lighter in comparison to the proton and thus is easilly deflected.

Question 5

12

Answer 5

12

Question 6

What is an isotope?

Answer 6

Isotopes are basically the atoms of the same element having the same number of proton or atomic number but different nucleon number. that means they have the same number of protons but different number of nuetrons

Question 7

Why do isotopes have the same chemical properties but different physical properties?

Answer 7

the isotopes have the same chemical properties because they have the same number of electrons and that makes them have similar chemical properties the physical properties such as mass and density are different because of the diffrerent number of nuetrons in each element. If a certain isotope has more nuetrons in comparison to its other isotope it will generally have a heavier mass and density ( since mass affects density as well)

Question 8

What are shells sub shells and orbitals in an atom?

Answer 8

In each atom the nucleus has shells at a certain distance from it (derived by principal quantum number). These shells contain sub shells ( S,P,D,F). These sub shells further contain orbitals in them (S. Px,Py,Pz. D1,D2,D3,D4,D5). Each of these orbitals have electrons spinning in them and each orbital can allow upto two electrons to spin in it.

Question 9

What is principal quantum number?

Answer 9

It decides a shells average distance from the nucleus. The higher the principal quantum number, The further the distance(from the nucleus) and energy of that shell.

Question 10

How do sub shell energies differ from one another?

Answer 10

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Question 11

In case of an ion which has electrons in the D and the S orbital. which electrons would be taken first?

Answer 11

Generally the electrons with the highest energy are taken first so the D sub shell electrons should be taken first however here an exception is made and the 4s electrons are taken first.

Question 12

How many orbitals does sub shell S, P, and D have ?

Answer 12

S: 1
p: 3
D: 5

Question 13

What is the shape of the S sub shell?

Answer 13

It is circular

Question 14

What is the shape of the P sub shell?

Answer 14

It is like the infinity sign or an “8”

Question 15

What is a free radical?

Answer 15

A free radical is the atom in which there is one or more unpaired electron, it is highly reactive due to that reason. `w

Question 16

Define first ionization energy?

Answer 16

It is the energy needed to make 1 mol of gaseous atoms to one mol of gaseous ions.

Question 17

Define Second Ionization energy? ( not asked in syll)

Answer 17

It is the energy required to make a gaseous mono positive ion into a gaseous Di positive ion. Second ionization energy is always greater than the first ionization energy

Question 18

identify and explain the trends in ionisation energies across a period and down a group of the Periodic Table ?

Answer 18

The first ionization energy down a group decreases as when you go down the group the number of shells increase and thus are further away from the nucleus and its attractive forces

When u go right across a periodic table the ionization energies generally increase as the number of protons increase and the overall nucleon charge increases and thus pull on electrons increase. HOWEVER, there are some exceptions (due to residual repulsions or changing sub shells or shells)

Question 19

Why is first ionization energy less than second?

Answer 19

Because in the second ionization energy the particle itself is a positive ion so it is difficult to remove the electron form a positive ion itself.

Question 20

What are the factors affecting ionization energy?

Answer 20

1) The nucleon positive charge
2) the distance of the electron from the nucleus
3) shielding effect ( screening of electrons).
4) atomic or ionic radius ( positively charged ion will increase ionization energy as it is difficult to remove electron from it)

Question 21

Why does Lithium have lower IE in comparison with Helium?

Answer 21

Lithium : Lithium has lower ionization energy than helium because it is screened by the electrons in 1s2 shell and is also in shell 2

Question 22

Why does Boron have lower IE in comparison to Beryllium?

and Mg less than Al

Answer 22

Boron has lower IE than beryllium because of the change in the sub shell. Boron’s valance electron is in P sub shell’s orbital while Beryllium’s valance electron is in S sub shell’s orbital. The P sub shell’s orbital is at higher energy in comparison to the S sub shell’s orbital and that causes electron from boron’s P sub shell to remove with ease and thus less energy. \

The same reasons occur for Aluminum as well.

Question 23

Why does oxygen have less ionization energy in comparison to Nitrogen even though it is on the right side of nitrogen in the periodic table. Same with Phosphorus and Sulpher.

Answer 23

This is due to the phenomenon known as residual repulsion. Due to Hund’s law the electrons in each orbital are put one by one instead of putting two together. So upon oxygen when there was no more space due to there not being an extra orbital. The electron had to be put in an orbital which previously had an electron causing repulsion between both the electrons ( residual repulsion). This caused the ionization energy of sulpher and oxygen to be less than their preceding elements.

Question 24

In an isotonic series what are the sizes of the atoms moving right across a group?

Answer 24

The sizes of the atoms decrease because as you move across the periodic table due to ions forming the number of electrons remain the same but the number of protons start to increase so the overall pull of the nucleus increases and the particle shrinks.

Question 25

What happens to atom size when moving from top to bottom of the group?

Answer 25

the atom size increases as there is addition of shells when moving top to bottom .

Question 26

How does every cation compare to its nuetral atom in terms of size?

Answer 26

The cation is smaller compared to its nuetral atom because the it loses an electron and thus the protons have less electrons to pull and charge increases so the ion shrinks and is smaller

Question 27

how does every anion compare to its neutral atom in terms of size?

Answer 27

the size of the anion increases as in an anion an electron is gained which causes the same amount of protons to now attract a larger number of electrons causing the pull to become weaker and thus the size of the anion to increase.

Question 28

What is Vsepr theory?

Answer 28

the theory states that in covalent bonds. The shared electron pairs repel each other. They repel each other to the furthest which causes the shape and angles between each bond pair to change according to the structure of the molecule. They can stability because of this.