CHAPTER-03

STRUCTURE OF MATTER

𝐙𝐀𝐗𝐦±

Expression Of Atom

Board Question 2019❖ 13

27Al3+ in this formula-

(i) Mass Number 27

(ii) Number of electrons 13

(iii) Number of neutrons 14

Which one is correct ?

(a) i, ii (b) i, iii (c) ii, iii (d) i, ii, iii

Poll Question-01

Expression Of Atom

❑ What is the actual mass of a proton ?

(a) 1.765 × 10−24g

(b) 1.75 × 10−24g

(c) 1.675 × 10−24g

(d) 1.673 × 10−24g

Board Question 2019

Isotope Isotone Isober

Structure Of Atom

Isotope → Equal number of protons

Isober → Equal mass number

Isotone → Equal number of neutrons

Relative Atomic Mass

❖ If the mass of an atom of a element is 2.66 × 10−23 g, what is the name of the

element? (Jessore Board -2020)

❖ Relative atomic mass = (Mass of one atom)

1/12 × C12

Average Relative Atomic Mass

𝐙𝐀𝟏𝐗 a%

𝐙𝐀𝟐𝐗 b%

𝐙𝐀𝟑𝐗 c%

Relative Atomic Mass

❖ In nature we get two isotopes of copper and they are 2963Cu and 29

65Cu respectively.

The average atomic mass of copper is 63.5 . Determine the percentage amount of

those isotopes.

Chattogram Board 2020(a) Define nucleon number.

(b) Why does relative atomic mass have not any unit ?

Relative Atomic Mass

The energy of the rotating electron radiates and

falls into the nucleus.

Rotating electrons

(i) Nucleus stays in the center of the atom, almost total mass of the atom is determined in nucleus.

(ii) Atom is charge-neutral. Equal number of protons and electrons stay in the atom.

(iii) The static electric attraction force between proton and electron acts like centripetal force and

because of this centripetal force electrons move round the nucleus like our earth does round the

sun.

Rutherford’s Atomic Model And Limitations

Bohr’s Atomic Model

1. Orbit of fixed energy

2. Angular momentum opinion-

mvr = nh

2π

3. Opinion for Electron shifting in orbits-

∆E = En2 − En1

Atomic Model

Event-1 : 1911 year (Chittagong Board -2020)

Event-2 : 1913 year

• Describe the importance of Event-1 in chemistry• Explain that- Event 2 is the corrected feature of Event-1

Orbit & Orbitals

Orbit Shell(n)

𝒍 = 𝒏 − 𝟏 Sub ShellNumber of Sub Shells

Number of

orbitals

Number of electrons in sub-shell= 𝟐(𝟐𝐥 + 𝟏)

Total number of electrons

K 𝐧 = 𝟏 𝐥 = 𝟎 𝟏𝐬 𝟏 1 𝟐 𝟐 × 𝟎 + 𝟏 = 𝟐 2

L 𝐧 = 𝟐𝐥 = 𝟎𝐥 = 𝟏

2s2p

2 13

𝟐 𝟐 × 𝟎 + 𝟏 = 𝟐𝟐 𝟐 × 𝟏 + 𝟏 = 𝟔 8

M 𝐧 = 𝟑𝐥 = 𝟎𝐥 = 𝟏𝐥 = 𝟐

3s3p3d

3135

𝟐 𝟐 × 𝟎 + 𝟏 = 𝟐𝟐 𝟐 × 𝟏 + 𝟏 = 𝟔𝟐 𝟐 × 𝟐 + 𝟏 = 𝟏𝟎

18

N𝐧 = 𝟒

Ca(20) =

Cu 29 =

Sc(21) =

Cr(24) =

Electronic Configuration

Chapter 04Periodic Table

Periodic Table

Periodic Table

Group 1 – Alkali Metals

Group 2 – Alkaline Earth Metals

Group 18 – Noble Gas

Group 17 – Halogen

Group 16 – Chalcogen

Name of Different Groups in Periodic Table

Determine The Position Of Element In The Periodic Table

Last

ElectronGroup Period

s The number of electrons of the last s Maximum no. of n

pThe number of electrons of p+ The

number of electrons of the last s + 10Maximum no. of n

dThe number of electrons of d+

The number of electrons of the last sMaximum no. of n

Periodic Table

A Si B S Cl

Dhaka Board 2020Portion of Periodic Table

[A & B are used here symbolically]

What is the period & group of ‘B’ element in the periodic table ?

(a) period-2, group-3

(b) period-3, group-15

(c) period-4, group-11

(d) period-6, group-12

Periodic Properties

1. Atomic Radius

2. Ionization Potential

3. Electron Affinity

4. Electro-Negativity

5. Metallic properties

❖ One energy shell is added when going downwards in a group .

Atomic Radius

Atomic Radius

In a period, from left to right electrons and protons increases though energy shell

remains the same.

𝐍𝐚 𝒈 𝐍𝐚+ 𝒈 + 𝒆−

Ionization Energy

𝐂𝐥 𝐠 + 𝐞− 𝐂𝐥− 𝐠

Electron Affinity

Electronegativity

Periodic Properties at a glance

Metals

Semimetals

Nonmetals

Electronegativity

Ionization Energy

Electron Affinity

Atomic Radius

Ion

izati

on

En

erg

y

Ele

ctr

on

eg

ati

vit

y

Ato

mic

Rad

ius

Ele

ctr

on

Aff

init

y

Solving Board Questions

Rajshahi Board 2020

❖ Among Na & Na+ which one’s size is smaller ? Explain.

Which one has the least ionization energy ?

(a) X (b) Y (c) E (d) G

Solving Board Questions

Answer the following questions :

Group → 1 2 17 18

Period 1 E

2 D

3 X Y G

Answer the following questions :

Group → 1 2 17 18

Period 1 E

2 D

3 X Y G

(i) Metallic property of Y is less than X

(ii) D is the most electronegative

(iii) Y can gain electronic configuration of G

Which one is correct ?

(a) i, ii (b) i, iii (c) ii, iii (d) i, ii, iii

Solving Board Questions

ElementElectron number in the last energy

level

A

B

C

D

𝟑𝐬𝟐

𝟐𝐬𝟐𝟐𝐩𝟒

𝟏𝐬𝟏

𝟐𝐬𝟐𝟐𝐩𝟓

Solving Board Questions

Determine the elements A, B, C & D [Board -2019]

LiNaCRb

Mg Al Si B AD

ClBrI

Solving Board Questions

• Explain the order of atomic size of A, B, C & D [Board -2016]

❖ Explain the order of atomic size of X,Y & Z [Board -2019]

Solving Board Questions

Element Electron number in the last energy level

X Has 2 protons less than Cl

Y Placed in 4 side right from Ca

Z Placed in period 4 and group 2

❖ Explain the order of atomic size of A, B & C . [Board 2018]

Element Period Group

A 2 14

B 2 17

C 3 2

Solving Board Questions

𝟗𝑷

𝟏𝟕𝑸

𝟏𝟗𝑿 𝟐𝟎𝒀 𝟐𝟏𝒁 𝟑𝟓𝑹

𝟓𝟑𝑺

Solving Board Questions

a) What is Dobereiner's law of triads ?

b) Why ‘Ar’ is called as inert element ? Explain.

c) Explain the order of atomic size from X to R.

d) Show with reactions that , “Elements of same group has same properties.”

[Dhaka Board -2020]