Problem Solving Session, Structure Of Atom

Slide 1: Introduction to Structure of Atom

Basic building block of matter
Understanding atom helps understand chemical reactions
Historical development of atomic theory
Key contributors: Dalton, Thomson, Rutherford, Bohr, Schrödinger
Structure of Atom - An Introduction

Slide 2: Dalton’s Atomic Theory

All matter is made up of tiny indivisible particles called atoms
Atoms of the same element are identical, while atoms of different elements are different
Atoms cannot be created, destroyed, or transformed into another element in a chemical reaction
Chemical reactions involve rearrangement of atoms

Slide 3: Thomson’s Model of Atom

Plum Pudding Model
Atom is a uniform, positively charged sphere with negatively charged electrons embedded in it
Discovery of electrons using cathode ray tube experiments
Thomson’s experiments on the deflection of cathode rays in electric and magnetic fields

Slide 4: Rutherford’s Model of Atom

Gold Foil Experiment
Most of the mass and positive charge of the atom is concentrated in a tiny region called the nucleus
Nucleus is positively charged, dense, and occupies very little space
Electrons revolve around the nucleus in fixed orbits
Most of the atom is empty space

Slide 5: Bohr’s Model of Atom

Planetary Model
Electrons revolve around the nucleus in specific energy levels or shells
Each energy level has a fixed amount of energy
Electrons can jump between energy levels by gaining or losing energy
Electrons in the outermost energy level are involved in chemical reactions

Slide 6: Quantum Mechanical Model of Atom

Wave-particle duality of electrons
Electrons can exist as both particles and waves
Probability distribution of electron density around the nucleus
Quantum numbers and orbitals
Pauli’s exclusion principle, Hund’s rule, and Aufbau principle

Slide 7: Atomic Number and Mass Number

Atomic number (Z) represents the number of protons in an atom
Identifies the element
Mass number (A) represents the total number of protons and neutrons in an atom
Neutrons play a key role in determining isotopes

Slide 8: Isotopes

Atoms of the same element with different number of neutrons
Same atomic number but different mass number
Isotopes have similar chemical properties but different physical properties
Example: Carbon-12, Carbon-13, Carbon-14

Slide 9: Electronic Configuration

Distribution of electrons in different energy levels and subshells
Follows Aufbau principle, Pauli’s exclusion principle, and Hund’s rule
Valence electrons and their significance in chemical reactions
Examples of electronic configurations for different elements

Slide 10: Summary

Structure of an atom includes a positively charged nucleus and negatively charged electrons
Dalton’s atomic theory, Thomson’s model, Rutherford’s model, Bohr’s model, quantum mechanical model
Atomic number, mass number, isotopes, and electronic configuration
Understanding the structure of atoms is crucial for understanding chemical reactions

Slide 11: Electron Configuration

Electrons occupy different energy levels around the nucleus
Each energy level can hold a specific maximum number of electrons
The energy levels are labeled K, L, M, N, and so on
The maximum number of electrons in each energy level is given by the formula 2n^2, where n is the principle quantum number of the energy level
For example, the maximum number of electrons in the K energy level is 2(1)^2 = 2

Slide 12: Electron Configuration Example 1

Let’s take the example of carbon (atomic number 6)
The electron configuration of carbon is 1s^2 2s^2 2p^2
This means that carbon has 2 electrons in the 1s subshell, 2 electrons in the 2s subshell, and 2 electrons in the 2p subshell
The total number of electrons in the carbon atom is 2 + 2 + 2 = 6

Slide 13: Electron Configuration Example 2

Let’s take the example of magnesium (atomic number 12)
The electron configuration of magnesium is 1s^2 2s^2 2p^6 3s^2
This means that magnesium has 2 electrons in the 1s subshell, 2 electrons in the 2s subshell, 6 electrons in the 2p subshell, and 2 electrons in the 3s subshell
The total number of electrons in the magnesium atom is 2 + 2 + 6 + 2 = 12

Slide 14: Valence Electrons

Valence electrons are the electrons in the outermost energy level of an atom
They are responsible for the chemical properties and reactions of the atom
The number of valence electrons can be determined from the electron configuration
For example, carbon has 4 valence electrons (2 in the 2s subshell and 2 in the 2p subshell)

Slide 15: Lewis Electron Dot Structure

Lewis electron dot structure is a notation used to represent valence electrons
The symbol of the element is surrounded by dots, each dot representing one valence electron
For example, the Lewis electron dot structure of carbon is: C: .
The Lewis electron dot structure helps in understanding and predicting chemical bonding and reactions

Slide 16: Periodic Table

Periodic table is a tabular arrangement of elements based on their atomic number and properties
It is divided into periods (horizontal rows) and groups (vertical columns)
Elements in the same group have similar chemical properties due to similar valence electron configuration
The periodic table provides valuable information about the elements, such as atomic mass, symbol, and electron configuration

Slide 17: Periodic Trends - Atomic Radius

Atomic radius is the distance from the center of the nucleus to the outermost shell of the atom
Atomic radius decreases across a period from left to right due to increased nuclear charge and stronger attraction for electrons
Atomic radius increases down a group due to addition of new energy levels and shielding effect of inner electrons

Slide 18: Periodic Trends - Ionization Energy

Ionization energy is the energy required to remove an electron from an atom or ion
Ionization energy generally increases across a period from left to right due to increased nuclear charge and stronger attraction for electrons
Ionization energy generally decreases down a group due to larger atomic size and shielding effect of inner electrons

Slide 19: Periodic Trends - Electronegativity

Electronegativity is the tendency of an atom to attract electrons towards itself in a chemical bond
Electronegativity generally increases across a period from left to right due to increased nuclear charge and stronger attraction for electrons
Electronegativity generally decreases down a group due to larger atomic size and shielding effect of inner electrons

Slide 20: Summary

Electron configuration determines the arrangement of electrons in different energy levels and subshells
Valence electrons play a crucial role in determining the chemical properties and reactions of an atom
Lewis electron dot structure represents valence electrons in a simple and visual manner
The periodic table provides important information about elements and periodic trends such as atomic radius, ionization energy, and electronegativity Completing slides 21 to 30 in Markdown format: ``markdown

Slide 21: Atomic Mass

Atomic mass is the mass of an atom in atomic mass units (amu)
It is determined by the combined mass of protons, neutrons, and electrons in the atom
Atomic mass is generally not a whole number due to the existence of isotopes
Atomic mass can be calculated using the weighted average mass of all the isotopes of an element
Example: The atomic mass of carbon is approximately 12.01 amu

Slide 22: Mole Concept

Mole concept is a fundamental concept in chemistry
A mole represents a fixed number of entities, which can be atoms, molecules, ions, or particles
Avogadro’s number (6.022 x 10^23) represents the number of entities in one mole
One mole of any substance has a mass equal to its atomic mass or molecular mass in grams
Example: 1 mole of carbon atoms has a mass of approximately 12.01 grams

Slide 23: Molar Mass

Molar mass is the mass of one mole of a substance in grams
It is numerically equal to the atomic mass or molecular mass of the substance
Molar mass is expressed in grams per mole (g/mol)
It can be used to convert between the mass, moles, and number of entities of a substance
Example: The molar mass of carbon is approximately 12.01 g/mol

Slide 24: Stoichiometry

Stoichiometry is the calculation of the quantities of reactants and products in a chemical reaction
It is based on the principles of conservation of mass and the mole concept
Stoichiometric calculations involve balancing chemical equations, determining mole ratios, and solving equations
Stoichiometry helps to analyze and predict the outcome of chemical reactions
Example: Given the balanced equation 2H2 + O2 → 2H2O, calculate the moles of H2O produced when 4 moles of H2 react.

Slide 25: Limiting Reactant

The limiting reactant is the reactant that is completely consumed in a chemical reaction
It determines the maximum amount of product that can be formed
The other reactant is called the excess reactant
Limiting reactant calculations involve comparing the mole ratios of reactants to determine which one is limiting
Example: In the reaction 2H2 + O2 → 2H2O, if 3 moles of H2 and 4 moles of O2 are present, which is the limiting reactant?

Slide 26: Percent Composition

Percent composition gives the relative mass of each element in a compound
It is calculated by dividing the mass of each element by the total mass of the compound and multiplying by 100%
Percent composition can be used to determine the empirical formula of a compound
Example: Calculate the percent composition of water (H2O)

Slide 27: Empirical Formula

Empirical formula represents the simplest ratio of elements in a compound
It is based on the percent composition or experimental data
The molecular formula represents the actual number of atoms of each element in a compound
Empirical formulas can be used to determine the molecular formula using the molar mass
Example: If a compound has a percent composition of 40% carbon, 6.67% hydrogen, and 53.33% oxygen, what is its empirical formula?

Slide 28: Lewis Structures

Lewis structures are diagrams that show the bonding and non-bonding electrons in a molecule or ion
Valence electrons are represented by dots or lines around the symbol of the element
Lewis structures help to understand the bonding and geometry of molecules
Octet rule is followed to ensure that atoms have 8 electrons in their valence shells, except for hydrogen (2 electrons)
Example: Draw the Lewis structure for water (H2O)

Slide 29: VSEPR Theory

VSEPR (Valence Shell Electron Pair Repulsion) theory is used to predict the shapes of molecules
It is based on the repulsion between electron pairs in the valence shell
The arrangement of electron pairs determines the molecular geometry
VSEPR theory helps to explain the polarity and physical properties of molecules
Example: The VSEPR geometry of water (H2O) is bent or V-shaped

Slide 30: Summary

Atomic mass is determined by the combined mass of protons, neutrons, and electrons in an atom
Mole concept and molar mass are used to calculate the mass and moles of substances
Stoichiometry involves the calculation of reactant and product quantities in chemical reactions
Limiting reactant, percent composition, empirical formula, Lewis structures, and VSEPR theory are important concepts in chemistry
Understanding these topics is essential for problem-solving and analyzing chemical reactions