Atom Module PDF

Atom Objectives Explain the basic concepts in general chemistry and familiarize with the different laboratory apparatuses used in the laboratory. Understand the fundamental concepts in general chemistry and differentiate between various laboratory apparatuses used in the laborato...

Atom Objectives Explain the basic concepts in general chemistry and familiarize with the different laboratory apparatuses used in the laboratory. Understand the fundamental concepts in general chemistry and differentiate between various laboratory apparatuses used in the laboratory. At the end of this module, the student should be: Classification of Matter Differentiate between pure substances and mixtures Explain the differences between elements and compounds Identify examples of homogeneous and heterogeneous mixtures Atom Models of an Atom and Subatomic Particles Describe the development of atomic models through history Identify the main subatomic particles and their properties Explain the structure of an atom using the current model mixtures Electron Configuration Understand the concept of energy levels and sublevels Write electron configurations for various elements Explain the Aufbau principle, Hund's rule, and the Pauli exclusion principle Periodic Table and Periodic Trends Describe the organization of the periodic table Define effective nuclear charge and its significance Explain periodic trends in atomic radius, ionization energy, and electronegativity  anything that occupies space and has mass. combination of two or more form of matter that has a definite substances in which the substances definite (constant) composition and substances and distinct retain their distinct identities. properties. Air 1 Mixture or Pure Substance? Air is a mixture, not a pure substance. The main components components of air are Nitrogen (about 78%), Oxygen (about (about 21%), Argon (about 0.93%), and Carbon dioxide (about (about 0.04%) 2 Homogenous or Heterogenous? Air is considered homogeneous because its composition is uniform. You can't see the individual components with the naked eye or even under a regular microscope. 3 CO2 is a component of air. Is it an element or a compound? CO2 is a compound because it contains two different elements: elements: carbon (C) and oxygen (O) Classify each of the following as an element, a compound, a homogeneous mixture, or a heterogeneous mixture: 1. seawater 2. helium gas 3. sodium chloride (table salt) 4. a bottle of soft drink 5. milkshake 6. air in a bottle 7. concrete States of Matter 1 Solid molecules are held close together in an orderly fashion with fashion with little freedom of motion 2 Liquid are close together but are not held so rigidly in position and position and can move past one another 3 Gas molecules are separated by distances that are large compared compared with the size of the molecules Discussion: 1. Using water as an example, what are the three states of matter, how can they be interconverted, and what are the key temperature-related terms associated with these transitions 2. How heat affects conversion between states? Atomic Model Billiard ball Model 1 5th Century BC Greek philosopher Democritus proposes the concept of of indivisible particles called "atomos" 2 1808 John Dalton formulates a precise definition of atoms, marking the beginning of modern chemistry 3 1799 Joseph Proust publishes the law of definite proportions, proportions, supporting Dalton's theory Dalton's Atomic Theory Elements and Atoms Identical Atoms Elements are composed of All atoms of a given element are extremely small particles called identical in size, mass, and called atoms chemical properties Compounds Chemical Reactions Compounds are composed of Chemical reactions involve only of atoms of more than one only the separation, element in simple whole- combination, or rearrangement number ratios rearrangement of atoms Laws of Chemical Combination Law of Conservation of Mass Definition Example Significance States that in a chemical reaction mass is If we start with 4 grams of hydrogen and This law is one of the fundamental mass is neither created nor destroyed hydrogen and 32 grams of oxygen, we'll principles of chemistry, providing a basis destroyed we'll end up with 36 grams of water. The basis for understanding chemical The total mass before the reaction (4g + reactions and stoichiometry. (4g + 32g = 36g) equals the total mass mass after the reaction (36g of water). water). Laws of Chemical Combination Law of Definite Proportions Definition Example Significance States that a pure chemical compound This means that in any sample of pure It provides evidence for the existence of always contains the same elements in water, for every 1 gram of hydrogen, atoms and molecules with fixed exactly the same proportions by mass, there will always be 8 grams of oxygen. structures and avenue to predict the regardless of the source of the composition of compounds and the compound or how it was prepared. outcomes of reactions. Laws of Chemical Combination Law of Multiple Proportions Definition Example Significance If two elements form more than one Carbon forms two compounds with This law provided further support for compound, the masses of one element oxygen: carbon monoxide (CO) and Dalton's atomic theory and the concept that combine with a fixed mass of the carbon dioxide (CO2). The ratio of of atoms combining in simple ratios. other are in ratios of small whole oxygen in these compounds is 1:2, numbers. consistent with the law. Identify the law that explains the following: 1. If you burn a log, the mass of ash + smoke = mass of log + oxygen used 2. Carbon and oxygen form CO and CO2. The ratio of oxygen in CO2 to CO is 2:1 3. Carbon dioxide is always 27% carbon and 73% oxygen by mass, no matter its source Discovery of Electron 1 1850s-1900s Investigations begin to reveal the internal structure of atoms 2 1890s Cathode ray experiments lead to the discovery of electrons electrons 3 1909 Millikan's oil drop experiment precisely measures the charge of charge of an electron Plum-pudding Model 1 Atoms were electrically neutral The cathode ray tube proved that atom contains electron. To electron. To achieve electrically neutral state, there must be must be some positive charge in atoms to balance the negative the negative electrons. 2 Development of the model Thomson proposed that the atom was a sphere of positive positive charge. Within this sphere, electrons were embedded embedded like plums in a pudding. The positive charge was was thought to be evenly spread throughout the atom. 3 Limitations It didn't account for the concentrated positive charge in the in the nucleus, which was later discovered. The Electron 1 Cathode Ray Experiments 2 Millikan's Oil Drop 3 Properties Experiment Electrons are negatively charged J.J. Thomson used cathode ray R.A. Millikan measured the precise charged particles with a mass of tubes to study the properties of precise charge of an electron using of 9.10 × 10-28 g, much lighter than of electrons, determining their using oil droplets suspended in an than protons or neutrons charge-to-mass ratio in an electric field Radioactivity Alpha (α) Rays Beta (β) Rays Gamma (γ) Rays Positively charged particles, deflected by Negatively charged electrons, deflected by High-energy electromagnetic radiation, deflected by positive electric fields negative electric fields radiation, not deflected by electric fields fields The Proton and Atomic Nucleus Thomson's "Plum Pudding" Rutherford's Gold Foil Nuclear Model Pudding" Model Experiment Rutherford proposed that atoms have a Proposed atoms as a uniform sphere of Alpha particles were scattered at large dense, positively charged nucleus sphere of positive charge with angles when fired at gold foil, containing protons embedded electrons contradicting Thomson's model Gold-foil Experiment 1 Unexpected Results A small fraction of alpha particles were deflected at large large angles, with some even bouncing straight back. 2 Discovery of the Nucleus The fact that some particles were strongly deflected suggested the presence of a small, dense, positively charged region within the atom. 3 Overturning of the Plum Pudding Model Thomson's Plum Pudding Model suggested that positive charge was charge was evenly distributed throughout the atom while the strong strong deflections observed were inconsistent with this even Nuclear Model 1 Concentrated Positive Charge This nucleus contains nearly all of the atom's mass. This explained the strong strong deflections observed in the Gold Foil Experiment, as the concentrated charge concentrated charge could exert strong repulsive forces on alpha particles. particles. 2 Mostly Empty Space The model suggested that the vast majority of an atom's volume is empty space. empty space. Electrons orbit the nucleus at relatively large distances, similar to similar to planets orbiting the sun. This explained why most alpha particles in particles in Rutherford's experiment passed through the gold foil with little or Nuclear Size 3little or no deflection. This vast difference in size explained the low probability of alpha particles hitting a hitting a nucleus, accounting for the small fraction of strongly deflected particles in particles in the Gold Foil Experiment. The Neutron Discovery Properties James Chadwick discovered Neutrons are electrically neutral neutrons in 1932 by bombarding particles with a mass slightly bombarding beryllium with greater than protons alpha particles Significance The discovery of neutrons explained the mass discrepancies between between different isotopes of elements Atomic Structure Particle Charge Mass (g) Electron -1 9.10938 × 10^-28 Proton +1 1.67262 × 10^-24 Neutron 0 1.67493 × 10^-24 Atomic Number and Mass Number Atomic Number (Z) Mass Number (A) Relationship The number of protons in an atom's The total number of protons and Mass Number = Atomic Number + nucleus, which determines the element's neutrons in an atom's nucleus Number of Neutrons identity Isotopes Definition Atoms of the same element with the same number of protons but different different numbers of neutrons Mass Differences Isotopes have different mass numbers due to varying numbers of neutrons neutrons Chemical Properties Notation for Atoms and Isotopes Standard Notation Example: Uranium Isotopes A(Z)X, where A is the mass number, Z is the atomic number, 235(92)U and 238(92)U number, and X is the element represent uranium-235 and element symbol uranium-238 respectively Hydrogen Isotopes Special names: protium (1H), deuterium (2H), and tritium (3H) Atomic Size and Nuclear Size Size 1 Atomic Radius 2 Nuclear Radius Typical atomic radius is about Typical nuclear radius is 100 picometers (pm) about 5 × 10^-3 pm 3 Size Comparison If an atom were the size of a sports stadium, its nucleus would be about be about the size of a marble Identify the mass number, atomic number, and the number of protons and neutrons 1. 20 11𝑁𝑎 2. 22 11𝑁𝑎 3. 178𝑂 4. 146𝐶 5. 36 17𝐶𝑙 Ions: An ion is an atom or molecule that has gained or lost one or more electrons, giving it a net electrical charge. Positive ions (cations): Atoms that have lost electrons Negative ions (anions): Atoms that have gained electrons Determine the number of proton, electrons, and neutrons. Also, identify the mass number and atomic mass. 1. 20Na +1 2. 64Cu +2 3. 32S2- 4. 31P3- 5. 27Al3+ The Modern Atom Nucleus Contains protons and neutrons, accounting for most of the the atom's mass Electron Cloud Electrons occupy the space around the nucleus, determining determining chemical properties Ongoing Research Our understanding of atomic structure continues to evolve with evolve with new discoveries in physics and chemistry Planetary Model Key observations He proposed that electrons orbit the nucleus in specific, allowed allowed energy levels. Development process He postulated that electrons could only exist in certain orbits orbits without radiating energy. Key aspects of the model Electrons can jump between these levels, emitting or absorbing absorbing specific amounts of energy. Quantum Mechanical Model Model Main concept Electrons don't orbit in fixed paths but exist in "probability "probability clouds" (orbitals). Uncertainty We can't know both an electron's exact position and momentum simultaneously. Experimental support The model successfully predicted many atomic properties and properties and chemical behaviors. Electron: Wave-Particle Duality Duality To describe an electron… Electrons are tiny and weird. We can't see them directly or or describe them like regular objects. We need a special way to way to describe where they are and how they behave in atoms. atoms. Quantum numbers They're like an electron's "address" in an atom. Each set of of quantum numbers describes a specific state an electron can electron can be in. Purpose They turn the fuzzy idea of electron "clouds" into something we something we can work with mathematically. Principal Quantum Number (n) Number (n) Represents the main energy level or "shell" of "shell" of the electron Can be any positive integer (1, 2, 3,...) Larger n means higher energy and farther from from the nucleus Example: n = 1 is the first shell, closest to the the nucleus Angular Momentum Quantum Number (l) Describes the shape of the orbital Values range from 0 to (n-1) Often represented by letters: s (0), p (1), d (2), f (3)Example: When n = 2, l can be 0 (2s orbital) or 1 (2p orbital) Magnetic Quantum Number (ml) Indicates the orientation of the orbital in space Values range from -l to +l, including zero Example: For a p orbital (l = 1), m can be -1, 0, or +1 Spin Quantum Number (ms) Represents the intrinsic angular momentum of the electron Can only be +1/2 or -1/2 Often referred to as "spin up" (+1/2) or "spin down" (-1/2) Electron Configuration Electron configuration is a way to describe how electrons are arranged in an atom. Principles of Electron Configuration Aufbau Principle Electrons fill orbitals from lowest energy to highest Hund's Rule For orbitals of equal energy, electrons will occupy separate separate orbitals before pairing up Pauli Exclusion Principle No two electrons in an atom can have the same four quantum quantum numbers Writing Electronic Configuration spdf Notation Orbital diagram Noble gas Notation spdf Notation 1. Determine the number of electrons: This is usually equal to the atomic number for neutral atoms. 2. Begin with 1s and work your way up the order. 3. Write the notation. Write the energy level number (1, 2, 3, etc.). Follow it with the sublevel letter (s, p, d, or f) then, add a superscript with the number of electrons in that sublevel. 4. Continue until all electrons are placed. Keep following the order until you've accounted for all electrons. Example: Oxygen (8 electrons) 1s² 2s² 2p⁴ Noble gas Notation 1. For larger atoms, use noble gas notation. Example: Sodium (11 electrons): [Ne] 3s¹ This means it has the same configuration as Neon, plus one more electron in the 3s orbital. Write the Noble gas notation of the following 1. I 2. Mg 3. Ba 4. Se 5. Fe Orbital Diagram 1. Know the filling order. (the spdf notation) 2. Draw the orbitals. Remember: s = 1 orbital, p = 3 orbitals, d = 5 orbitals, f = 7 orbitals. 3. Fill with electrons. 1. Use arrows to represent electrons. 2. Up arrow (↑) for spin up, down arrow (↓) for spin down. 4. Follow the Aufbau Principle. Fill orbitals from lowest energy to highest. 5. Use Hund's Rule. For p, d, and f orbitals, fill each orbital with one electron before pairing. 6. Apply Pauli Exclusion Principle:Maximum of two electrons per orbital, with opposite spins. Example: Oxygen (8 electrons) 1s: ↑↓ 2s: ↑↓ 2p: ↑ ↑ ↑ Draw the orbital diagram of the following. 1. O 2. Zn 3. K 4. F- 5. Ca2+