Periodic Table Overview

• Groups/Families: Vertical columns (1-18) with similar chemical properties.

• Periods: Horizontal rows (1-7) indicating energy levels of electrons.

Key Groups

• Hydrogen

  • Reactive, colorless, odorless at room temperature

  • 1 outer level electron

• Alkali Metals: Group 1

  • Extremely Reactive, never found in nature in pure form

  • Silver Colored and Shiny

  • Density so low can be cut with a knife

  • 1 Outer Level Electron

• Alkaline Earth Metals: Group 2

  • Slightly less reactive than alkali metals

  • Silver colored and more dense than alkali metals

  • 2 outer electrons

• Transition Metals: Groups 3-12

  • Moderate range of reactivity

  • Wide range of properties

  • Shony and good conductors of heat and electricity

  • Higher density and melting points

  • 1 or 2 outer level electrons

• Halogens: Group 17

  • Nonmetals

  • Very reactive

  • Poor conductors of heat and electric

  • Tends to form salt

  • 7 outer level electrons

• Noble Gases: Group 18

  • Unreactive nonmetals

  • Colorless, odorless gases at room temperature

  • Small amounts

  • 8 outer level electrons

• Boron Group: Group 13

  • Reactive

    • Most abundant metals in the earth’s crus

    • 3 outer level electrons

• Carbon Group: Group 14

  • Varied Reactivity

  • 4 Outer Level Electrons

• Nitrogen Group: Group 15

  • Varied Reactivity

  • 5 Outer Level Electrons

• Oxygen Group: Group 16

  • Reactive Group

  • 6 Outer Level Electrons

Metalloids

• Elements with properties of both metals and nonmetals have properties intermediate between metals and nonmetals. The commonly recognized metalloids are:

  • Boron (B)

  • Silicon (Si)

  • Germanium (Ge)

  • Arsenic (As)

  • Antimony (Sb)

  • Tellurium (Te)

  These elements are found in groups 13 to 16 of the periodic table.

Lanthanides and Actinides

Elements 95 through 103 are manufactured in a lab and do not exist in the lab

• Lanthanides

  • Shiny

  • Reactive

• Actinides:

  • Radioactive

  • Unstable

Dalton's Atomic Theory

• Matter is composed of atoms.

• Atoms of a given element are similar to one another and are different from atoms of other elements

• Atoms of a given element are identical in mass and properties.

• Compounds are formed by a combination of different atoms.

  • Particular compounds are always made of the same kinds of atoms and the same number of each kind of atoms

Definition of Atom

• The smallest particle of an element that retains its chemical properties.

Characteristics of Atoms

• Chemical Symbols: One or two-letter notation for elements

• Mass Number: Total number of protons and neutrons in the nucleus.

• Atomic Number: Number of protons in the nucleus, defines the element.

• Neutral Atoms: Equal number of protons and electrons.

Isotopes

• Atoms of the same element with different numbers of neutrons.

Nuclear Symbol

• Represents an isotope with the format:

  • ( A ): Mass number, Superscript

  • ( Z ): Atomic number, Subscript

  • ( X ): Chemical symbol of the element.

    Molecular Basics

    • Molecule: A group of two or more NONMETAL atoms bonded together

    • Formula: Represented by molecular formulas where number of atoms of each element are subscript

    • Covalent Bonds: Bonds formed by the sharing of pairs of electrons between atoms.

    Ion Basics

    • Ion: An atom or molecule that has gained or lost one or more electrons, resulting in a net charge.

      • Cation: A positively charged ion (loss of electrons).

        • Metal Atoms

      • Anion: A negatively charged ion (gain of electrons).

        • Nonmetal Atom

    Key Points

    • Molecules can consist of the same or different elements.

    • Ions are crucial in chemical reactions and electrical conductivity.

AMU (Atomic Mass Unit)

AMU is a unit of mass used to express atomic and molecular weights. It is defined as one twelfth of the mass of a carbon-12 atom.

1 AMU = 1.673 × 10^-24

History of the Atom

Mendeleev

• From Russia, used playing cards with atomic properties

• Developed modern periodic table

Democritus (Ancient Greek)

• Proposed the concept of atoms as indivisible particles

• Coined the term "atomos" meaning uncuttable or indivisible

John Dalton (Early 19th century)

• Proposed elements are made of specific atoms

• Suggested atoms combine in specific ratios to form compounds

• Measure the mass of things

• Split water up into hydrogen gas and oxygen gas,

  weighed the gases and found that the mass of oxygen

  was always eight times heavier than the mass of

  hydrogen.

  • Law of Definite Proportions

J.J. Thomson

• Discovered the electron using cathode ray tubes

• Electromagnetic fields, and cathode rays are negatively charged.

• the subject is illuminated not by light, but by electrons, shorter wavelength than visible light, so they are capable of imaging much finer and smaller details

• Proposed the "plum pudding" model of the atom

  • Positive charge inside but also have negative charges embedded

Ernest Rutherford

• Conducted the gold foil experiment

• Shot alpha particles at gold foil

• Few went through, some deflected and some bounced

• Discovered the nucleus, had a positive charge, because positive particles were being shot back

• Proposed the nuclear model of the atom with positive electrons in the middle, and negative electrons going around the outside of the nucleus, most of it is easy

James Chadwick

• Discovered the neutron, took longer no charge

Niels Bohr

• Proposed electrons orbit the nucleus in specific energy levels

• Positive charge on the inside, negative charge on the outside

• Electrons travel on the outside in specific orbitals

• High Energy to Low energy levels

Erwin Schrödinger

• Introduced wave mechanics to describe electron behavior

Werner Heisenberg

• Bohr and Schroignder were right

• Electron is a particle but is desired by Scroginder’s idea of wave (Quantum Theory of Atom)

Vocabulary

Element: A pure substance consisting of atoms with the same number of protons in their nuclei.

Shell: A group of orbitals with the same principal quantum number, representing the main energy levels of electrons around an atom's nucleus.

Sublevel: A subdivision of an electron shell, corresponding to different orbital shapes (s, p, d, f).

Orbital: A region in an atom where an electron is likely to be found, described by a set of quantum numbers.

Orbital notation: A method of representing electron configuration using boxes or lines to show orbital occupancy.

Quantum number: A set of numerical values that describe the properties of electrons in atoms.

Ground state: The lowest energy state of an atom or molecule.

Excited state: A higher energy state of an atom or molecule, typically unstable and short-lived.

Photon: A particle of light or electromagnetic radiation.

Electronegativity: The tendency of an atom to attract electrons in a chemical bond.

Ionization energy: The energy required to remove an electron from an atom or ion in its ground state.

Ionic radius: The effective size of an ion in a crystal lattice.

Oxidation: The loss of electrons by an atom, molecule, or ion.

Reduction: The gain of electrons by an atom, molecule, or ion.

Stable octet: An atom with eight valence electrons, typically associated with noble gas configuration.

Kernel: In atomic physics, the nucleus plus the inner electrons that are not involved in chemical bonding.

Elements

Elements

• First is capital, second lowercase

• 118 known

  • 91 that occur naturally

Atoms

• This can be seen through atomic force microscopes

Radiation and Radioactive Decay

Radiation - Parts of atoms that are given off or energy that’s given off by radioactive atoms

• Measure it with a Geiger counter

  • Has been hit by a piece of radiation gives off a bit of electrical charge that can be picked up

• Hear static because of background radiation

As a number of protons increases more neutrons are needed to keep it stable. The nucleus is held together by something called the strong nucleus force.

Alpha Decay

• Positive Charge

• α

• Helium - 4 (2 protons 2 neutrons)

  • Nuclide

• So weak can’t go through paper

• Nucleus is very large and have too few neutrons

• Atomic number decreases by 2 and mass decreases by 2

Beta Decay

• Negative Charge

• β

• High Energy Electron with a charge of -1

• Stopped by aluminum sheet

• Neutron mits high energy electron that changes and gains a proton

• Atomic number increases, no change in mass

Gamma Decay

• Neutral Charge

• γ

• Every radioactive disintegration

Artificially Created in Lab

Positron Decay

• Positive Charge

• Anit-particular electrons

• β

• Electron with a charge of 1

• Stopped by aluminum sheet

• A proton is changed into a neutron and releases a positron

• Atom decreases by 1, mass stays the same

K-Electron Capture

• The nucleus absorbs atom electron

• The proton is changed into a neutron

• The atomic number decreased by 1, mass stayed the same

• Only in atoms with atomic number higher than 20

Nuclear Chemistry - The study of how nuclei of unstable isotopes undergo changes to become more stable, the changes occur with the emission of large amounts of energy

N:P Ratio

• Lighter Elements

  • 1:`

• Heavier Elements

  • 1:5

Half-Life- Amount of time for half the radioactive particles to undergo decay

Half-Life Equation - N(t) = N(0)(1/2)^t/t_1/2

Artificial Transmuations (Bombardment Reactions) - Occurs in laboratory

• Stable nuclei are converted to one that is radioactive and then decay into stable products

• Medical Purposes

• Bombarding Particle

  • Neutron

  • Charged Particle

Rate of Radioactive Decay

• Number of atoms decaying in unit time

• Measured in

  • Curies (Ci) - 3.700 × 10¹⁰ atoms/s

  • Becquerels (Bq) - 1 atom/s

Binding Energy - Energy required to tear apart a nucleus by separating protons and neutrons in the nucleus or the energy released by nucleons combining to form a nucleus, a measure of stability

Nuclear Fission

• Nucleus splits into smaller fragments, each with higher nuclear binding energies

• Bombarding a large heavy nuclear with a smaller one

• Atomic bomb and nuclear reactions, mass is lost

• Mass goes to energy

Chain Reaction - Self-sustaining nuclear or chemical reaction from which the product of one step acts like a reactant

Critical Mass - Minimum amount of fissile material needed to maintain a nuclear chain reaction, the sample must be large enough so neutrons react with more of the sample than escape

Nuclear Fusion

• Two nuclei combine to make a heavier nucleus

• Low masses fuse to form heavier more stable nuclei with higher binding energies

• Large amounts of energy

• Powers the Sun, hydrogen bombs